I decided just to keep the second meter, the 270 series 3, intact. It had a few issues, but now it's working fine. Comparing its DC and resistance readings to those of two other known accurate DMMs, the Simpson is a little bit off. I need to recheck the readings to see if they're within the error range. Assuming they aren't, I'd like to calibrate this myself, but from looking at the U.S. Navy and Simpson procedures, I'd need a calibrator and power supply, neither of which I have. Am I correct in assuming there aren't any other ways to execute this myself without these tools?