Hmmm. The symbols are actually a collector's device to identify the fakes that sprung up. Yes, the producers of the fakes got away with it as long as they did not copy the symbol, but I don't know if that is only because Hasbro chose to look the other way, or if indeed they only copyrighted the symbol. Is there, to your knowledge a statement from Hasbro stipulating that the symbol alone is copyrighted and the actual image is basically public domain? If so, then certainly you are in the clear. If not, it's a fine line.
I can check some legal texts to see if I can find evidence of Hasbro bringing action against anyone, and what that particulars and outcome were. If they had brought action against any of the manufactures of the imitations, and it was dismissed, that would be a good indication. In the meantime, it might be a good idea to consult with a copyright attorney. Some of these big companies are happy to pounce and it would probably be more economical to do all the official checks and be sure your ducks are in a row, so to speak, rather than go through all the production set up costs to possibly end up facing a cease and desist. Even if you won, such an action could substantially cut into your profits.
Also, I have not been active there recently, but I do belong to some forums that dealt specifically with copyright and licensing issues. I can search through there to see if this particular product came up if you'd like.
I'm just concerned that you would have poured your heart and soul into this, and invested money in production only to have Hasbro drop a wall in front of you. I would hate to see that happen to anyone. I only bring this up as an offer to help as I do have some resources available, not to admonish you at all, and please don't think that I'm trying to tell you what to do. Certainly, how you proceed is totally up to you, but it's a strange (and litigious) world in which we live and it's always good to know folks are trying to watch your back for you.
Bev