I went for this deal. The ad says it's an RCU810B, and that's what the package that they sent says, but it's only a RCU810A. Open the battery cover & ther's no JP1 connector & there's a label that says RCU810A.
I called MCM & they said they'd send out the correct unit, and they didn't even make me send the first one back. The second unit that arrived was the same RCU810A. Perhaps this is why they're surplus & cheap.
I've called once again & they said they'd check what's in the warehouse. I may end up with 2 of these for free. I'll just have to solder in my own connector.