Mike. Peter,
In all honesty, without checking, these things probably go for under
$50 posted, or I wouldn't pay any more, put it that way.
It would cost $20 bucks driving around finding suitable alum stock
to make a few and that's before I added my machining time.
If I were you I would buy one, it would be in the post 2 days later
and probably better tolerance and finish than mine
Have I talked you out of it yet
As for reflective innards, all you can see in the pics are the M42 thread
surfaces and the inner and outer inteference fit sleeve.
The bore is a vee shaped tool run on slow thread cutting down the guts
as I do all my adaptors. Flat black paint and texta to touch up.
Sweet as.
Steve