To clarify, by a “standard” keyboard I mean a (usually US) QWERTY PC keyboard with 101 to 105 keys (depending on the amount of Win/Super and Menu keys and the presence of an additional punctuation key to the left of Z). Those have three rows of three keys each above the arrows (not counting any “media keys” such as Power); the topmost one of those is PrintScreen / SysRq, Scroll Lock, and Pause / Break, though some of those labels may be omitted. I honestly have never seen a full-size PC keyboard without those. (How am I supposed to hit Ctrl-Break or Win-Break otherwise?)

Strictly speaking, there is no Break key in the same sense that there is no SysRq key—there are only special Break and SysRq scancodes that AT and PS/2 keyboards send instead of Pause and Print Screen when Ctrl or Alt respectively is depressed (thus the combined labels), while USB keyboards don’t even have those, they just send normal modifier sequences. But I don’t think that’s what you had in mind :)