[morzh]

A smaller inner diameter pipe can be turned and the excess marterial removed making it thinner wall larger opening tube.

Exact copies are rarely made of off-the-shelf parts.
If the cap does not face you (like in Philco 70 or 90 where it is up front) small discrepancies will not be noticed unless looked at closely.

If someone were to set out to produce an exact replica, he could possibly use the stock parts but then he'd need some specialized equipment to do some more work than simply cut a piece of pipe annd slap a cap on it.