For E110 portable Rockwell Testers, I am most familar with Wilson's M-1. Often referred to as a "C-clamp" tester, it uses a full 150KG major load using a spring-laoded load cell (for the 'C' scale) and a diamond braile indentor. It is capable of producing results nearly as accurate as a bench tester, but it is a bit more complicated than a bench tester and more difficult to use. I had to calibrate them myself on a daily basis (I couldn't even get my technicians able to calibrate them). They are good instruments, but you really have to know how they work and be willing to work on them to get reliable results. Even the metallurgical equipment calibration services we used couldn't calibrate them (all they could do is punch a block and slap a sitcker on them; if they couldn't get a good reading, they had to send them back to the factory).
If you are dealing large forgings, why aren't you using a Brinell tester? The King Portable Brinell tester is a mainstay in the forging business and I would generally trust a King Brinell result more than a Portable Rockwell. True, even a King tester is operator dependent (and I have seen more people mis-use portable testers more than I've seen them use them correctly), but it is much easier to train someone to use one over a Wilson M-1. With Brinell, you have to have a good surface, or you can't read the impression, which makes it a bit more fool-proof. Of course, having to read the impression is more difficult than reading a dial (or, I guess, perhaps digital readouts with today's technology), but it isn't that difficult to do.
I've used the Equitip testers quite a bit, too. They are good for letting you know if a material is hard or soft, but if you needed to know if a part is 30-36 HRC, I'm not sure I'd trust them. Either the M-1 or King tester can give you that confidence.
rp
