Item references in catalogs are numbers for some catalogs, but for many important catalogs they aren't numbers. If they were numbers then KM# 62.1 and KM#62.10 would be the same, but they aren't the same. And “A2” in “KM# A2” isn't a number, and neither is “ 1-552Aa” in “HMZ 1# 1-552Aa”.
This is issue is considered in the guidelines. The phrase “the alphanumeric code” is used in sections 3.2.11 and 4.2.12 to talk about the reference codes in catalogs. But other places become imprecise and use the phrase “reference number” instead of “alphanumeric code”, “reference code”, or “reference identifier”.
Numista should have a common term for catalog identifiers which is used everywhere – throughout the guidelines, in the “Add or modify data” page (which currently says “Reference number” when talking about the pair of the catalog identifier and the coin identifier), and probably other places.
(Talking about Numista numbers isn't a problem as those values are always numbers.)
(The French guidelines aren't as detailed as the English guidelines, but they use “Numéros de référence”. The guidelines for Spanish Numista are currently in English, including saying “Use English unless otherwise specified” instead of specifying Spanish.)
