Who's writing the books?

[wmoebis]

Yes a long time ago they changed cell size. Most the ones you find now are the 3 inch. Not sure if charts work on the 2.5's or not. I wouldn't bother with them. Elev are usually accurate and if you check your sample against them you will know if yours is accurate.
I get both CGC moisture tests and protein test samples to check my moist and protein machine. If you can find them.

[Mjolnir]

I purchased a Shore model 920 several years ago. Just as accurate as the 919 we have in the shop and quite a bit handier for checking samples in the field.
http://www.shoremeasuring.com/index.shtml
I got mine at Falman Sales. The new model is the 930 with integrated scale.

[hobbyfrmr]

Labtronics 919. Coop or flamans sell them I think around 1200.00
So you have to ask yourself "was this running around with uncertainty about a rejected btrain for moisture worth $1200.00 ?".
Is the hassle of a moisture rejected btrain coming back home to you to put back in the bin, in -15c weather worth less than $1200.00?