The first number denotes the line.

Toms were like TT908_ _ for a model number; FT916_ _ for a floor tom and BD922_ _ for a bass drum (underlines are two letters that I have no idea what they mean. They happen to be RC on my drums which I thought was for 'Recording Custom' but they are either for the color code, or something else.)

The first example would be a recording custom ("9" tells you that- pre Recording custom was 9000 series) 8 inch diameter tom. Next is a 16" Floor tom, also Recording Custom, and finally a 22" bass drum. The letters of the serial number tell you the year it was made.

EDIT> and the badges do look the same, but the recording customs were a coppery tiny and the others were all silver from what I remember.

I meant to say "coppery TINT" in my edit. Here's a poor picture of a RC tag on my early (Jan 89 build) bass drum:

On the later drums they stuck the tag to the shell and had a seperate air hole, even in the bass drums (I never understood this on the bass drums??).

This was done when they switched to YESS mounts and the tom air hole was under the mount location.

Toms always had two tags on them, a real one and a dummy one, so that no matter which way you mounted the toms, you could see a tag. Floor toms and bass drums had one tag each.

They sure look like mid-80's Stage series drums to me!

http://www.vintagedrumguide.com/images/catalogs/yamaha/1983_yamaha_catalog_8.jpg

OK I have been digging into this now, because the letters after the numbers for the model has been bugging me.

I always thought the RC was for recording custom, but I had seen other recording custom drums with different letters after the numbers.

And now I have a handle on it.

The RC on my drums (and all standard depth RC drums made before ~94 when the YESS mount was introduced) does signify Recording Custom.

POWER recording custom (deeper depth) had RF after the number, except drums like the 8", 16" FT and 18" FT because these were the same in both lines. I have also seen RP (which makes sense for the POWER designation) on an actual drum so perhaps the RF was a typo in the catalog for part numbers...

Once the YESS mounts came out, the letters changed. Standard depth drums were denoted YJ (J for Jazz I guess?) and the (now deeper as standard) RC's with YESS mounts had simply the letter Y after the numbers.

Later more lines had the YESS mounts, but at the time only the RC drums had them.

I hope to compile this information and put it into a usable chart or something to decipher the letters and numbers on the drums...

Those are great drums ! I think they were constructed better than the moderD' Drummern day Stage Series, that line would have competed with the early Tama Imperial Stars.

Thanks everyone for the great insight. I need another drum kit like I need a VD, but it's sooo tempting. An addiction that I'm finding hard to deal with lately.