I won't vouch for the price, but this new listing in Rock Ridge is certainly the epitome of what "Old" Greenwich mansions are expected to look like
/16 Rock Ridge Avenue, 1928 construction, 3.4 acres, asking $11.9 million (I told you I wasn't going to necessarily endorse its price). From time to time over the past couple of decades, I've had clients who've come to Greenwich from disparate parts of the world, and when I've brought them to houses like this, they almost invariably say something like, "now this is what I envisioned in a Greenwich house!"
And it really does hit almost all the buttons (except for its one-car garage, but there's certainly land enough here to correct that): an 8,300 square foot main house, a 2,400 sq.ft. guest house, and isn't it amusing to reflect that 2,400 sq. ft. is larger than the average house in real America, set on beautiful grounds, in a private association.
I love this house, and while I'd rather sell it to a client than just admire it here, I do hope it will go to someone who will treasure a house of this era.
(UPDATE: I haven't seen this house yet, but the absence of pictures of its bathrooms and master bedroom make me suspect that there's work to be done there. Not a deal killer, certainly, but something to be considered when negotiating its price.)