Here's pictures of the 2 tang, plugs ,with a ruler for comparo.
Some of you guy's might know more about the.
maker. Thanks Dave
Both measure 1 1/16 ACF
top and bottom are 3/4 16,center is 5/8 18 Center has allen head cleanout plug.
3/4 16 has a tapped hole in side of tang, to lock barrel I assume.