I didn't want to put this on the LM399 10V reference thread as it is slightly different, and it isn't about the design anyway.
Having bought one of RoadRunner's voltage references:
https://www.eevblog.com/forum/buysellwanted/deeu-simple-lm399-reference-board-improved-second-version/a while back, yesterday I finally got around to encasing it.
I included a LT3402 board for the 15V and also a L7818CV to feed it 18V and allow more leeway for the input voltage (the LT3402 doesn't like more than 20V and I might want to use a 24V supply - efficiency doesn't matter much because the current drawer is so small).
I have had it running for about a day now and the Voltage reading for my 2015 varies (after warm up) between 9.999991 and 9.999997 and my 2000 tracks it but about 0.000002 or 3 higher. This is well within the 1day spec and I've not had a calibration for years (the 2000 is most recent and that was in February 2014).
I need to set up an RS232 or GPIB connection and plot the results properly but that will have to wait until I've finished my Oscillator measurements (I'm more into time-nuttery than Voltage-nuttery at present).
Photos show the 15V voltage, the 18V voltage (as checks), the casing and the 10V reference measured on various Voltmeters I have.