You haven't really provided enough info to help you to identify it. Is it a box lock or a side lock gun? Makes a HUGE difference in price.
The side lock is called a Sauer Artemis. Should have H&H type side locks with Greener crossbolt double underlugs, double sear safeties, selective single trigger, selective auto ejectors. Came in Grade I with fine line engraving and Grade II with full English arabesque engraving.
Grade I about $4300 and Grade II about $5300 in the condition you mention.
Or if a box lock price would run about $1450.