I thought this was a really interesting question - and a pretty tough one, too! Google didn't help at all, and the old lists of undocumented DBCC commands don't help, because DBCC LOCK used to not have any parameters.
Responding to AFPeterson's post, this could be very useful ... but I'll PM you so as not to spoil the question for anybody else.
I actually had to test the thing out to figure out what it did exactly. That's probably what made it such an enjoyable question for me - the fact that it was something that I didn't know and couldn't look up in BOL, but I could test it at least. My biggest surprise is that 65 % of people have gotten it right so far! Either this is a nice parameter that I just didn't know about (and 65% of everybody else did!) or it's an easy question to guess, or ... maybe Frank's post helped some people? But I already knew what the 3605 did ...