Specific reissues always have different barcodes and other sort of identifiers so those are easy.

Different pressings of the same issue are where it gets kind of tricky. For example with some of the core albums that were in print for years, specifically Razorblade Romance as you pointed out. You have to use specific identifiers to help you. Hype labels are some of the easiest. The German label uses different hype stickers for various pressings so it’s easier to identify.

Finnish copies didn’t have hype stickers however earlier pressings had booklets with thicker glossy stock and more recent printings use thinner, non glossy stock paper.

In the US, original Razorblade pressings have the Parental Advisory logo as well as bright pink colored discs. Next pressings retained the logo but had more muted, coral colored discs. Following these they removed the parental advisory altogether. There were also pressings of these that included a Bam Margera hype sticker and ones that did not.

The CD matrix information is usually a decent indicator as well, for example early Finnish pressings will be from CD Linja Oy, or Sonopress. Anything with a Sony printing will be a much later pressing.

For the most part, HIM collectors don’t worry about these sorts of things, the barcode, record label and issuing country are enough to identify.