wanted Vref based on LK1000 ideally using xdev design yielding 1ppm quality

[johartley2001]

hello

hello I'm involved with calibration work and am looking for a standard to verify a 6.5 digit DMM, does anyone know where I can buy a ready assembled & tested Vref?

it's seems like the xdev design the best option of is there a better option ie the design used in the HP3458A

many thanks please email on johartley2001@yahoo.com if you have info thanks