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Originally Posted by Agraf

This is probably the film titled Uschi Bondage, 8mm color loop running 9:43, estimated to have been made in 1979, converted to DVD and distributed under the general title "Uschi Digard Wrestling Vol. 2" by Bygone Media.

From what I can see in the background, this film served as the basis for a glossy «number-one-and-only» collector's magazine," Uschi in Bondage" sold in the USA for $7,00, which cover is already in this thread. The whole magazine is dedicated to her: «...in which a legendary entertainment star comes over to get in bind after bind (seven binds to be exact)»

She was featured in the bondage magazine "Helpless", vol.1 no.2, published by Pinnacle Publications (USA 1974). I do not know if it's a different session, or the same above - in what case the date of the loop would have to be brought back to 1974.

Judging by the name of the clip i.e. UD-BTIB.avi it is actually more likely from the Alpha Blue Archives "Big Tits in Bondage" featuring Uschi. The rest of your facts are probably correct and likely Alpha Blue Archives got it from the same original source as Bygone Media.