Any of the Spanish gunmakers built guns to order on a regular basis. You may call it a "one-of-a-kind", but that doesn't increase the value or desirability. The Germanic touches of sling swivels and a cheekpiece are deducts in the value in today's market. Also, I must say your gun looks unusually new for a piece from that era, with what appears to be no actual use whatsoever. Regardless, I'm guessing maybe around $4500 would be a retail value.
JR

Last edited by John Roberts; 01/03/25 12:45 PM.
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