There are 2 rectangular metal fixtures--one on each side of the inside shell, that allow for the band attachment. I love the old world elegance of the M15. I've owned several in the past but not currently. With the 100th anniv. of WWI coming, I think I'll hunt up a nice one.
PS.....it may be 4 attach. fixtures, its been awhile since I fiddled....I believe they are soldered(?).....front, back, and sides (?) Somebody with one can do a follow up post on this issue.