Otto:
Would you oblige us with some images of the dreiläufer as well as the marks? If both of the longarms were altered pre-1946, then you may have cornered the market on 7X75R.

Under "Share This Photo" on Photobucket there should be 4 image choices:

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Direct Link
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Which one are you selecting to post the link?

Kind Regards,

Raimey
rse