Thanks for posting that Dean.
Unfortunately we can't inquire exactly where "junction of chamber & forcing cone" WT was measured.
If that is the "end of the chamber" (toward the muzzle; not breech) .068" is well below CIPs recommendations of .075" for a 20g with “Standard Steel” (Non-alloy AISI 1045) with tensile strength = 101,526-123,137 psi
Crolle damascus tensile strength averages about 55,000 psi or 1/2 that
Austin Hogan observed that factory small frame Parker 20g and 16g gun may have an end of the chamber WT < .090"
.068" is also well below
any measurement documented here
http://parkerguns.org/forums/showthr...096#post158096
http://parkerguns.org/forums/showthr...?t=1565&page=4
It might be very interesting, and prudent, to repeat the "end of the chamber" WT measurements.