Hi Lisa,
I'm glad you found us. I've modified your profile so your real name shows on posts as that is required.
I've never seen this pattern, prototype, or whatever it is. I'm convinced that it is a real piece made by Griswold, probably during the 1940's. I would call it a prototype which might be sent to the patternmaker so he could make a pattern to match the prototype. (You need a proper pattern for mass production). Just how Griswold made up this piece I don't know but I might assume that they cast a piece in brass from an original, large TM pattern, then modified the prototype piece by brazing on the handle which is a newer design than the original pattern had and also engraving the new small TM and other markings on the prototype while filling in the older markings (large TM, etc.)
As to worth, the starting price doesn't seem out of line but I don't think anyone but a willing buyer and your seller can really determine the worth or actuall price that the piece will sell for. There are those who might value this one-of-a-kind piece which, in previous production form, is already a hard to find, in demand, and expensive piece. But it's not a piece of iron cookware so it might take a special buyer or several people to value it highly enough to pay the going price. Only time will tell if it will sell. What I've said is only my opinion about the piece. I hope others will chime in and give their opinions. Definitely a very rare, very interesting piece but that doesn't necessarily mean that it is worth the asking bid or anywhere close.
Steve
