You'll almost always find the model information on a Walbro carburetor stamped into the body on the side opposite the jets. Most of the time, you'll find the number right beside the body. The carburetor here is a Walbro WT-99.

Occasionally, you'll find the carburetor model number in the second position below the body type, as illustrated here. This one is a Walbro WT-227F.

Zama carburetors are slightly more complicated. You're going to be looking for body type and the model number on opposite sides of the body. You'll find the body type on the same side as the jets, usually cast into the center of the housing. In this case, our carburetor has a "C1U" body. For the model number, you'll simply turn it around to the opposite side. It looks like this carb is a C1U-K26B.

Tillotson is an interesting make to work with. It can sometimes be hard to definitively identify one, so we've put together some extra information here.  On the smaller HU series, you're looking at the air filter side of the body. For the model number, you'll usually find a regular stamping- "40D" in this case. For the body, look inside one of the circles. Here we see "HU." This must be a Tillotson HU40D.

Uh oh. It appears as though we can't find the body type for this Tillotson carburetor. What we do have is the model number, and that's just fine! This is actually an "HS" body carb. What we have here is a Tillotson HS225A, as evidenced by the "225A" stamping on the side of the body opposite the jets, right there with the throttle and choke linkage.

A common theme among a lot of the larger small engine carburetors is that you'll typically (but not always!) find information stamped into the side of the mounting flange. Here, we have a Tillotson "HL" body carburetor marked "222B". This very obviously means that we've got a Tillotson HL222B.

I mentioned earlier that you won't always find the body type on a Tillotson carburetor. There are a few reasons for this, chief among them being that the equipment manufacturer has requested that it not be present. Fret not though! This is a photo depicting the common Tillotson body styles.