It’s not mine, and I’m not selling it. This is simply a curiosity questions–plus the opportunity to drool if nice pianos are your thing.
Our next door neighbor, Les, is an old (like 90) jazz guy, plays vibes mostly, but his step-dad worked at Steinway, and left him this piano. It’s a 1906 Steinway 6’ (or so) baby grand, signed by Mr. Steinway. It was factory restored in the 40’s and is in excellent shape.
Any guess what that puppy is worth? I’m guessing about the same as my house. 
Well, first of all - drool!
Second of all - you (or your friend) should buy the book Steinway, the Making of a Grand Piano, by Barron (I think - off the top of my head).
Bottom line is that I can’t remember when the Steinway design fully “crystallized” - some earlier models have features that are now considered UNdesirable and would only value the piano if it can be “upgraded” to have the features they have come to expect. Also, I know that some parts, if left unmaintained, can cause problems - that doesn’t sound like what happened here since you said it was refurbished in the 40’s. BUT - that can have its own problems, if the refurbishing ended up affecting some aspect of the piano that is a basis for it’s value.
In guitar circles, it is not uncommon for someone to have sent a guitar to Gibson, say in the 70’s to get it worked on - and they refinished, re-necked or otherwise re-something’d the guitar that strips out a huge chunk of the value that guitar would now have as a collector’s item.
This is all a way of saying: drool! But a lot of research is required.
IF the piano is in playing and collector’s condition, and is a highly-desired model, then, yeah, it could be worth a lot of money. Here’s to hoping it fits in that category!
Good guess.
It seems that well cared-for Steinways are worth right about the same as a new Steinway. In the case of a 6-foot grand, that would be in the rough area of $30,000 - 50,000 if you were buying it from a piano dealer. I’m not a piano collector, so I have no idea if being signed by Mr. Steinway is worth anything or not.
Aren’t they all signed by a Mr. Steinway?
It certainly is in excellent playing condition; I sat down an plunked a bit of Billy Joel. Les, of course, played a bit of jazz for us. As to collectability, I obviously couldn’t say.
Piano: The Making of a Steinway Concert Grand - James Barron
I’ll see if I can get him a copy as a gift. He’s a great guy and an excellent neighbor.
That book is a definite must read.
Also, there are various Steinway posters. I got my music ed/pianist daughter a couple a couple of years ago - one is a beautiful photo from above of an open grand, and the other is essentially an illustrated complete parts list. Couldn’t find anywhere to buy one, so I contacted the company and they sent me a couple of copies of both gratis.
There is another series of books - entilted something wacky like “Pianos” - which ballparks values for just about every brand of piano.