My first thought was Alder, but then I looked up the TL-72 and knowing what was common for MIJ Fender during those years I'm going to say Basswood, maybe Poplar. Probably Basswood.
Poplar is classified as a hardwood--because it's hard. Not as hard as maple, but harder than most pines.
Pressing a dent into poplar with a fingernail is not easy, so it could be poplar.
Poplar (which is not actually from poplar trees, it comes from Liriodendron Tulipifera) is quite soft. The terms "hardwood" and "softwood" are misleading, softwood just means it's from a conifer. Softwood may be harder than hardwood- southern yellow pine is harder than "poplar".