I had a Summarit that had an adapter locked on it - most likely by glue or locktite or something similar. It took ages to get the thing off since of course I was wary of breaking anything. From memory in the end I placed the lens in a Leica M lens cap , got a towel for grip and then twisted applying firm steady pressure. It did yield. But of course it all depends on the type of glue.
You can try a solvent, but if its epoxy then I am not sure that anything dissolves it. But locktight, crazy glue and so on all dissolve in acetone. I cannot now recall if I did this, but I know I considered it. It may be possible to gently drip a few drops of acetone onto the edge of the ring and let it sit for a while before trying to twist it loose. Moderation in quantity is key as the last thing you want is for it to get inside the lens where it can leave traces on glass. Acetone is available in hardware stores - or some nail polish removers have it also although I think in a more dilute form and many removers no longer have it at all. The special thinnners that can be bought for automotive paints might also work.
Problem is that it may be that the summaron needs access to the rear of the lens to loosen screw to disassmble it. (I have a couple of models of this lens but I am not at my home so cannot check.) Otherwise you could get a technician to disassemble the lens and then it could be possible to use heat on the offending parts once the glass and delicate inner workings are our of the way.
Incidentally the models I have are the late coated crew mount version of the same vintage as yours and the later fist M mount version which has the same optics, I believe. Both have an excellent reputation and I personally like their results which can be described as typicla of Leica lenses in that era - high resolution and low contrast. However like many Leica lenses of the era they are prone to developing haze in the inner elements due to the lube used in the lenses at that time. My M mount one has this issue but the other does not. A CLA usually fixes it in any case.
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