http://www.sakatavegetables.com/home...anum-Red-Robin
Sakata sells it but I don't see that they claim to have bred it and it is definitely OP. If you look through their catalog ( just click on "next variety" on this page to see) any tomato that is a hybrid is specifically labelled so with the name thoughout their website. Interestingly they sell it in both their ornamental and their vegetable listings and it is unusual in not being a hybrid since most everything else they sell is.
Not sure if RR is an actual heirloom but it has been around for a while for sure and every seed company I have seen that sells it sells it as an OP or doesn't specify hybrid. I have grown it myself from home saved seed received in swaps.
Enjoy your little mato's they are very cute plants
I recommend to Check out the micro tomato threads here on TV Bettaponic, there are some busy breeders developing new ones, blacks, yellow, pinks, multi-flora, all kinds of things coming out of their work and they are often looking for folks to help with grow outs if that interests you.
KarenO