I see stamped numbers, can you inform us which one tell us if it is a 18 or 23 spline?

There is a partial VIN number
A trans model number: PP833
A 10,000 day calendar build date: 3155 (March 18th 1970)
A consecutive build number: 0077

There is (was) a large stencil painted on 3 digit number that is the last 3 of the part number, but not always remaining for us to read today. Not too,sure that every year of the 833 trans had that painted number.

The cast in in raised numbers are for the individual pieces but they do not define the assembled transmission.