A method for those without a decent "macro-capable" camera, and / or, whose hands may be a bit shaky:

If you own a flat-bed scanner, try the following:

Cut a hole that is just a little larger than the head in a sheet of A4 or similar sized paper or thin card and lay it on the scanner platten. Try different coloured paper to see what works best for contrast etc.

Stand the case / cartridge in this hole and do a "test run".

Most scanner drivers / software enables you to "define" a "target" area and, of course, resolution.

Thus, you can minimise the fooling around in "cropping", etc.

If you are careful, you can line up the "top" of the headstamp with the "top" of the scan on screen. This saves a lot of fooling around in Photoshop or whatever software you are using, to make all your scans look "uniform".

Another "hint" is to have a "rule", calibrated in your choice of metric or Imperial, that can be stuck, "face-down" on the platten and under the masking sheet. This should appear in your scanned image and will make comparisons and scaling a lot easier.

If anyone has a method that is less "fiddly", I'm all ears.......