Allograft merely means a tissue graft of some sort from the same species (as opposed to a porcine heart valve, for instance, which is from a different species).
There are bone allografts, demineralized bone allografts, and skin allografts, all of which can be freeze dried. There are also Bone Morphogenetic Proteins, which is coded as an allograft, but isn't technically an allograft. Oh yes, and amniotic tissue is used as an allograft for wound healing.
From your answer, it still isn't clear if this is bone, skin, demineralized bone, or something else.
Since you suggested C1762 as one possible code, it could be connective tissue. But pretty much everything I've described can be called connective tissue.
All of this is why I asked for more information. And that's what I'm asking... what is the allograft specifically, and how was it used in the shoulder surgery?