What is this S here?

[YENKO DEUCE REGISTRY]

S ='s Stuff! What's the baseplate from? Plates are stamped 172.

http://i61.photobucket.com/albums/h68/aacorp/Holley%20parts_zps3hcqf0db.jpg (http://s61.photobucket.com/user/aacorp/media/Holley%20parts_zps3hcqf0db.jpg.html)

[Mr70]

Do you mean the butterflies are stamped 172?
Think those came std. on a Holley 750/800 doublepumpers.

[YENKO DEUCE REGISTRY]

Yes, the butterfly plates. Is it a '70+ version with the large vacuum port?

[Kurt S]

I just went through this with some baseplates that I have.
What's the numbers stamped and cast on the plate? They are probably on the corners nearer the throttle lever.

[ds1]

Looks like a 3310 vacuum secondary