340 T/A head identification

I understand that they came on T/A challengers, and AAR cudas on 340 six packs, and that they use offset rockers due to the pushrod holes, but I am wondering the story behind my heads. they have no O,U,J casted into them, they don't have 360 cast above the valvespring like the ''J'' heads do, and it has a casting number, but it isn't 915, and I cant even really read it. As far as the way the heads are made, they are correct. I found the lack of markings strange, and was wondering if anyone has seen replacement, or over the counter T/A heads before to back up the story of the guy I bought them from, or if they were a prototype casting or something crazy like that.