Sorry for digging up this old thread, but I made some more versions based on my real parts:
also see here: https://rebrickable.com/parts/3660/slope...tud-holes/
- 3660c: normal hollow stud and flat bottom pin and ridges
- 3660d: medium hole and round bottom pin (this version has a wider lip than the others)
- 3660e: small hole and round bottom pin
- 3660f: small hole and flat bottom pin
in addition to the existing ones:
- 3660a: normal hollow stud and round bottom pin (does this variant even exist in reality?)
- 3660b: stopper ring and flat bottom pin and ridges (this is the newer version, i only have this in dark bluish grey, 3660c only in old dark grey)
Based on that the c and f are the most common old versions we should check our printed versions (they are mostly with the b version which is too modern for the prints).
also see here: https://rebrickable.com/parts/3660/slope...tud-holes/
- 3660c: normal hollow stud and flat bottom pin and ridges
- 3660d: medium hole and round bottom pin (this version has a wider lip than the others)
- 3660e: small hole and round bottom pin
- 3660f: small hole and flat bottom pin
in addition to the existing ones:
- 3660a: normal hollow stud and round bottom pin (does this variant even exist in reality?)
- 3660b: stopper ring and flat bottom pin and ridges (this is the newer version, i only have this in dark bluish grey, 3660c only in old dark grey)
Based on that the c and f are the most common old versions we should check our printed versions (they are mostly with the b version which is too modern for the prints).