Joined: Dec Tue 29, 2015 8:23 am Posts: 139 Location: Australia
I know a few people - volt-nuts & general metrology nuts, as well as pros - who have the gear to accurately measure that. One of them owns a set of fixed standards ranging from 0.00001 ohms up to 10Tohm.
The high-value ones are used to characterise/calibrate things like high accuracy meggers, high impedance voltmeters, pH meters, geiger counters, etc. That one looks like one of the Russian military standards, but it may be a knockoff.
Stable standards like that ain't cheap, even in fixed form. For a switched standard, if it's the real deal and meets the claimed accuracy it's probably not too bad a price...