I agree with Lancaster. All the C96 carbines shown here were at least restocked and rebarreked quite recently. The barrels seem to be too long as the known originals were 14” maximum usually. The crucial difference of C96 pistol and carbine actions: on the carbine actions the pistol grip was part of the detachable buttstock. It was joined to the action body by a horizontal dovetail, locked by a left to right push button. This one seems to be the only one that shows this arrangement:

It may be an original carbine action or a pistol action remachined by a very good craftsman.
This one is obviously a converted pistol and was described as such in the auction:

On these two the crucial parts are unfortunately covered by the price tags, but the left one is apparently a converted 1930s “Schnellfeuer” pistol due to the detachable
magazine.

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