Three unusual and hard to ID eyepiece or optical adapters

Auction No.:
Current Bid:
High Bidder:
Marcus Saldanha
Bid History:
2 Bids
Fairbanks, AK - US
Michael Castellini
04/03/2021 10:33PM
04/10/2021 10:33PM
Buyer pays shipping
I have had these adapters in my optics miscellaneous drawer for years, and still have no idea how they are used. If you recognize any of them, then perhaps this auction will be a real find for you!

1. The largest has male 41mm threading @ very fine pitch about 0.5-0.6mm. On the female side, it has a diameter of about 48.5mm at about 0.75mm, definitlely more coarse than the male end. Path length is about 23mm

2. Next sized ring is heavier and of an older generation.  It has a T slit compression ring on the male side, but this is smaller than 1.25 inches and about 1 1/8 inch diameter. For an older style of eyepiece? On the female side, the threading is about 33mm diameter, at about 0.75  pitch.

3. The smallest ring is the strangest of all three:  Male threading at about 37mm diameter and about 0.5mm ultrafine threading on the external threading. The internal threading is 28.5mm and is threaded to accept a regular 1.25 filter.  My guess is some type of filter holder adapter to allow 1.25inch filters on a larger optical (37mm?) optical device. It has pin wrench tightening slots. 

S&H will be $4.50 to any of the 50 States
Foreign S&H @ actual  

Good luck with your bids.