Hi Martin,
Thanks for good review of DMM Check Plus and overview of other Voltage Standards products, I enjoyed it very much. As one of Doug's customers I can confirm I'm happy with his products and his service (sometimes you don't get both from same place).
If I had a wishlist I'd like to see all of the values noted on PCB so you don't have to refer to the paper reference, eg. DMMCheck has no current on PCB (there is no voltage either but I assume it's always 5.0000V), DMMCheck Plus has very little data on PCB. I think it would be just nice to use the standards without referring to paper certificate with measured values.