Here's what I believe is a 1912 Waterloo Boy engine, 2 1/2 HP (flywheels are 22" in dia, piston is 4 1/4" ).  
These greasy-engine pix are from the day I brought it home from the barn (June, 2011); I've cleaned it up a bit since then, but still have more to do.  I've since obtained a correct reproduction crank guard, too.

The gas tank says simply "The Cub", and looks like a nice farmer fix; I think this comes from an old Coldwell Cub lawnmower.  
I've picked up a solder-on spout and cap from Lee Pederson to attempt to fix this.

You can see this apparently started life as an ignitor engine, and someone has converted it to a spark plug.

The spark plug was finger tight, and when I took it out, it seems it had never been used. I'm wondering if this spark plug conversion was abandoned, and the engine put into storage at that time.  I later noticed that this is a nice take-apart plug!

Not sure if this is a factory spark plug conversion trip mechanism, a third party kit, or some sort of farmer fix associated with the spark plug conversion- it is very cleanly made. I have several photos of WB engines, and none have this sort of trip.
(Update) someone has identified this roller thing as a Model T ignition part!

Sold by Weaver Hardware, in Rochester!  I believe that store went out of business in May, 1918.

Here's the silvery "shield" decal on the hopper, which I can't quite read. In the sun, I can see that the scroll on top says "The Waterloo (something...)"

I actually bought this Dobson butter churn first, from the same barn- it is the very one that this engine used to run:

Oh, while I'm at it, here's a Waterloo Boy price list I found at the public library- what a great find!!  This engine cost $68 new.  Note the mounting options- Wood skids, Hand-Portable,  Horse-Portable, or Iron Sub-Base.
Waterloo Boy Price List Waterloo Boy mounting options

making progress with getting the cast iron pulley collar off.  I gently drove a screwdriver in between
the collar and the flywheel, and it's now 1/2" out from where I started.

I succeeded in removing the pulley collar tonite by gently hammering in ever-wider chisels,
plus applying Liquid Wrench as I went, then finishing it off with a wooden block hit with the hammer,
hundreds of times.  :-)  I can see that the jib key has no head (surprisingly), and that it has
some shims under it that look like they've backed out a bit.  I suspect this is why it's loose.
I don't see any cracks in the flywheel, thankfully. The gib key has a little play side to side
as well- I can just fit a .010 feeler gauge in there.

I finally got some time to work on this engine.  I used a plastic putty knife and managed to scrape off the 80 year old dried grease from half the engine.  I want to scrape off as much dry grease as I can before I start to use a cleaner or oil the engine.  I wiped off the oiler and found it's a nice brass number 3 (size), made by G.B. Essex Brass Co., Detroit, Mich.  
Before I bought it, I noticed one flywheel was loose a tiny bit- I could rotate it a bit on the shaft.. I've taken off the pulley and its collar, and found out why- the key seems to be about 3 thousandths too narrow in width.  Plus, it's got a metal shim for height.  It also has no head; will be difficult to get out.  

So today I tried (again) to get the gib key out of the loose flywheel- I was using vise grips, a pry bar, and tapping.  I then noticed that the keyway on the shaft had a ding in it where the pulley set screw had damaged it.  I got a very thin Dremel cutoff wheel and gently ground the channel straight, that worked!, I got it out!  It was clearly a hand-made key.  It was not driven thru to the other side of the flywheel hub, what was in there was too short.  You can see the hunk carved out of it to accommodate the pulley collar.  The other flywheel has a key with a head on it, but it's nice and tight, but does have a shim under it.  I'm going to leave that one alone!  Here's the key I removed:  

I later figured out that the reason it had no head was so that the pulley collar would fit tight against the flywheel.

Rob Gill (on helped me figure out what size key was correct for this engine, and I ordered a couple new ones, professionally made, from Hit and Miss Enterprises.  Before I install the new key, I need to remove the flywheel and clean and de-burr the gib key channel in the crankshaft and in the flywheel.

7/21/14 update:
Finally got a Round Tuit again... there is no damage to the shaft or flywheel collar or key channels. A while ago I got a correct, tapered replacement key with a head (from Hit and Miss)- two in fact- a 3/8" X 3.5 inch and a 3/8" X 4 inch (whichever one worked best I was going to use), plus some .002" shim stock, just in case. I cleaned the key channels wonderfully- the key slides smoothly on both shaft and in the collar.

I have absolutely zero experience with gib keys, and I had imagined that I'd put some bluing on the new key, slide it in, tap it, then check and lightly file until I got the fit perfect. Nice plan, but I find that the brand new key won't fit in the flywheel collar slot, AT ALL- the key seems too tall. When I line up the flywheel and shaft channels, the height of the resulting key hole is a smidge shorter than the tip of my new key. The tip of the key is ~0.336" tall.

I'm supposing that I will need to carefully, evenly, file down the non-tapered bottom side of the key until it fits in, but I'm not sure how much material to file off the key.  I don't know what a proper fit should look and feel like.

New gib key not fitting

Feb-May 2015 update:
I finally got some time to work on this engine again this Spring.  As noted above, it turns out that the brandy-new absolutely correct gib key didn't fit my particular engine.  The width and length were perfect, but it was too high, and I couldn't even get it started into the flywheel hub slot- see photo above.  I now have researched how it's supposed to fit and feel; I needed to mill it down some more.  And I don't own a milling machine.  Last summer, I didn't have any measurements of my actual setup (I wasn't prepared for the milling to happen so soon), but my friend Al S. from the Marion engine club took a stab at it.  He milled it down nicely but the milling machine was at his house and the engine at mine, so we couldn't actually try it and fit it on the spot.  Once home, I found that was much better, but would still only go in about 1/4 of the way- not nearly enough.  I thought hey, no problem, I can just file it down- and I tried just that.  Holy cow.  I had a very sharp file, and believe me, it would take a month of daily filing to take off as much as I needed.  I needed to mill it some more.  This time I bought a digital caliper and took very precise measurements of what I needed (the key is tapered in height).  Al lives pretty far from me, so I put up a sign at work this Spring asking if anybody had a milling machine, thinking that somebody might have a metalworking hobby.  5 minutes after I put up the sign, Bob B. showed up and that's when I discovered that there was a milling machine just down the hall at my workplace!  This was quite surprising as we work with software, and who would have guessed that they had a milling machine kicking around for hardware prototyping?  Half a lunch hour later, it was milled again, and when I took it home it slid in perfectly.  Then I discovered that the slot in the crankshaft was .007" wider than the slot in the flywheel; I hadn't noticed that before.  the flywheel width was perfect. 7-thou was plenty of slop for the flywheel to still be loose.  So I took an old stainless steel feeler gauge- a really long one- and cut it with snips. I slid it in next to the key and tapped it in.  And... the key dragged the shim all the way in and crumpled it at the end.  Sigh.  Pull key back out (I found I had an oddball chisel that worked perfectly for this; maybe it's an old gib key puller, who knows), back to the drawing board.  Cut a new shim.. there's no room to grab the end to keep it from being dragged in (and I didn't want to oil the key), so I made the shim L-shaped, so that it would just catch on the outside of the flywheel.  This worked perfectly.  I tapped the key all the way in (well, as in as I wanted to go), with the shim the entire length inside the crankshaft slot.
      [insert new key photo here]
      [insert key removal tool photo here]

7/11/15 update:
I'm really trying to get this engine running before my local club show at the end of the month. There is a very nice farmer-fix fuel system on this engine (using an old Coldwell Cub lawn mower gas tank) that I love, but the gas tank has no top.  I have a new cap and neck I picked up from Lee Pedersen, but I need to take it to a radiator repair shop to see if they can sweat it on; I don't have equipment or skill to do that.  In the mean time, I wanted to take the Cub tank off and attach a temporary tank between the flywheels in back (where the Waterloo Boy gas tank would normally go).  I have a good modern (well, 1970s) rectangular tank with fuel shutoff from my neighbor's junked snowblower.  Now that the old fuel piping is removed, I find that the iron elbow that connects the Lunkenheimer mixer to the head is loose at the head.  Loose by about 1/4 turn.  You can't just tighten it a quarter turn because then the mixer would not be hanging at the proper orientation.  Not quite sure what I could use to tighten it up- maybe some teflon tape.  I've asked the Smokstak guys for advice on this.  While taking things apart I discovered that there is an inline check valve marked:
    [insert check valve photo here]
I wonder what this check valve originally went to.  It rattles nicely, so it seems like it's going to be ok.
I also discoverd a lot of debris blocking the fuel line for several inches up near the tank.  I was wondering if this junk fell in after the tank cap was lost or if this was the reason why the engine was retired by the original owner- plugged fuel line.  (The Cub tank has no filter screen.)