These horns are commonly called "S.A." or "18 - 20" models, because of the engraving on the bell. This is incorrect. "S.A." is translated as "Anonymous Society" -- or a better English translation is "Incorporated". "18 - 20" is part of Buffet's address.

In any event, the name sticks -- and I prefer it to calling these horns "Series VII" or "Series VIII" (i.e. they're the 7th and 8th models Buffet ever produced), as I had in the past :)

These are the most elaborately engraved of all the Buffets ever produced and there were two variations available -- but only significant difference I can see between the two is that one set of horns has sheet-metal keyguards and one set has wire keyguards (based on other companies' horns, I'd say that the sheet metal horns are slightly newer).

The serial number ranges for these horns is based essentially on a "best guess": I know the introduction date of the Super Dynaction, the Dynaction model logically preceds that, and these horns precede the Dynaction, so I'm taking it "on faith" by some of the sources where I got these pictures that the date ranges are more-or-less accurate.

In any event, it is known that there was a fire in the Buffet plant around 1940 and all serial number data was destroyed -- possibly more than once. These horns seem to have started with a s/n of 1 or 100, continued until around 1xxx and then the sheet-metal keyguards were introduced -- and those horns started with a serial number of 1 or 1000 and also continued until around 1xxx.

It's possible that both the sheet-metal and wire-keyguard horns were available at exactly the same time and the production was so variable because of shortages of parts during WWII and thereafter -- but I recall hearing of someone with a horn with wire keyguards and a 21xxx serial number ...

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Techie Notes:
- Bell to body brace looks like it's "suspended": this was probably done to provide extra resonance for the bell notes (this feature was discontinued on the Dynaction, but was reintroduced on the S1).
- Keyed range from low Bb to high F.
- RH bell keys. This becomes standard for all Buffets from here on in.
- LH "pant guard" appears on horns equipped with sheet-metal keyguards.