Ah, but two different suppliers.
I did that because I was hedging my bets, in case one turned up with a 584J on it or something.
Now I just need to decide how to case them up. I've got quite a few expired devices that could donate their housing, but finding one that's just right might take me a while.
I see no need to put them in a metal case, but I do want to automate the switching of the reference outputs, using some of the hundreds of old telecoms relays I have.
I also don't want to use a mains power supply, so it's batteries. Might have a look on Hobby King to see what they've got in the bargain bin atm.