Charles,
The markings on the Borchardt you describe could be on of the Pen State rifles. You may be able to verify this by contacting Dr. Richard J. Labowskie who is the current owner of he Sharps Company records. Some of the Serial numbers are missing from the books relating to the Borchardt's but they may be there as they were an early production model. The Doctor will advise you for free over the phone, so have pen and paper at hand. If the new owner wants a letter corroborating the details it will cost him several hundred dollars.

I'm sorry I cannot recollect the Doctors address or phone number but someone on this Forum will know it and chip in with it. Good luck.
Harry Eales.