The trick is determining if a scale is accurate. Certified weights can cost more than the scale to be calibrated.
So, you make your self your own darn check weight! Stop by a junk yard, pick up a chunk of heavy steel that you can cut down to ABOUT 40 ounces. Perhaps a heavy angle iron or even a short length of i-beam. Just using a bath scale, lop off pieces until you get between 2.5 and 4 pounds. When you go to a big match with a calibrated scale, have them weight your check weight. Write the weight on a label on the chunk.
Then, if you get a cheap kitchen scale to do your own weighing, start by weighing your chunk and calibrate scale to read out that weight, and to read 0 when the scale is empty. You will be almost perfectly calibrated to weigh a 1911 then.