Mats posted pictures of his MrRef voltage and current reference PCB build. This tool helps check the accuracy of your multimeter:
Since my Agilent 34401 is currently out of calibration I didn’t bother installing the fine-adjustment trimopot. The 6350 is good for 0.02% (1mV) without any adjustments. But I installed two 10K 0.05% resistors on the board to get the 1mA output working.
The idea of using two cr1216 in each battery holder kinda works (I need >8 volts to run the chip so I have now four 3v cells in series), but the next revision of the board will use four separate battery holders. It’s too easy to short out the two positive poles of the batteries in the holder, I had to insulate them with kapton tape to get it working properly.