I contacted Webmaster Checks last night and they got back to me this morning. The "JCash" on the stub refers to "JuggCash" (Brazzers' webmaster program.)
Usually it's Mansef Productions. And this new cheque is printed on Bank of America paper.
I started to suspect it was JuggCash last night after looking at the stub more carefully. It looks like they may have abbreviated JuggCash to JCash because there isn't enough room in the column where the program's name is written.
So, that solves that