The serial number indicates that your piano was built in 1910.
Old pianos have no value just for being old. In other words, prospective buyers are not collecting pianos; they want to be able to play them. Pianos have parts that wear out and must be replaced, and a piano that hasn’t been regularly tuned will not hold a tuning. So, old pianos are at a disadvantage in the market.
Pianos are valued heavily on age after other factors like style, maker and condition. Age will tell you what kind of wear the piano would have mechanically. Even if the outside looks good the internal mechanisms are likely only in fair condition.
So, it's a plus that your piano has been regularly tuned, but it undoubtedly is in need of restoration. Even the Steinway company will tell you that.
In its present unrestored condition, the current retail (replacement or insurance) value of your piano is approximately $18,000. If you were to sell it, you could expect to get the fair market (private sale or auction) value of approximately 40% of the retail amount, or $7,200.
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