It's still a pretty hard question to answer, given how specific model numbers are sometimes missing on sales listings, and silent revisions to hardware.

in most cases you can tell at a glance. We have run into vendors changing their internals without any way of telling other than opening the cam up. Last year mos vendors started moving their cameras from the T31 processor to the newer (cheaper) T23, without changing model names. I've bought at least one cam where one user got an Ingenic chip and I got some random ARM chip.. and a few cases where they have a few wifi chip options and its a coin toss which one you get. When possible I try to account for this in my installers, so that the user doesn't need to deal with it themselves, but other times its unavoidable.