adash, the color reversible process is a special process, with two developer, which can give you surprises with fresh film, let alone the film have about 20 years overdue. With a recommended process.
Until November 1990 Orwo films were those that could be found on the market. When I not found color negative film, I buy Orwochrom UK 17 or 18 that I developed in negative color process (Orwo 5166 or 5188).
The results were good.
If you have TSS - chromogen substance, you will probably be able to develop your film like negative easily.
Risk, for me, when using the negative process is much smaller.
If you have not TSS, you can test the - CD 2, CD 3, CD 4 (chromogenic substances).
If you need recipes Orwo (9165 or 5166/5188) I can send you.