I've handled more than a few glocks, and own a glock 19, 29 and just acquired a 1st generation glock 17.
I must say that the first gen glock 17 feeler far slimmer than any others that I have shot or owned. The smoother grip makes it slightly slimmer.
I measured it against my 2nd gen glock 19, and it's only a hair slimmer, but the smooth rounded grips make it feel so much slimmer!
I would call this slim frame.