AS MANY of you know I rebuild MANY of these of AFB's.
I have been rebuilding them since I bought my Riv. new in 1964.
As I remember the tags never had a number on them.
The tags were all a certain color which denoted/identified the particular carb. that came on an original car/body.
MAYBE some of the earlier AFB's had numbers on them, but not as I remember.
In an answer to your question I remember they were mounted in the rear.
Looking at the carb. standing looking at it from the front the screw is mounted on the right rear at the is 2 O'clock position.
Tom T.