Some thought: Well the MDA codes for UK seem to be the heir apparent. Although I was amused to see the MLA comment on their site “Please note that an MDA Code is exclusive to the individual organisation, and should not be used for any other purpose.” I have no idea what it is meant to mean – unless the Deal museum code of “DEATH” (really!) means that I cannot write this sentence unless it is under the threat of “cannot say this”.
As with all code systems we now have the problem of letting other countries join in (Add your own joke about the European Uniion here). Luckily language can be used to differentiate different museum systems except for “global” languages like English and French where it is unlikely that there are coding systems available to differentiate Australian from American museums. What might be worth knowing is if Europeana has a museum naming system which would cover 27 (26?) countries – but I suspect it may be overly complex.
OR. If the museum code is unique then you may not need the language code as British Museum=English (for rare cases you could still allow the museum to specify an undefault language where they might have a special exhibition in Welsh). This would mean that the 5 character MLA code would in most cases be a 3 character addition.
Other unique and short(ish) systems would be their primary IP address in Hex. Which would be 6-8 extra characters but would be international and scalable.
So if we have a table that provides a look up from a registered IP address to a GLAM name and its default language then we could do this for an extra 6 characters (8 minus the 2/3 character language code). Does 6 extra characters to define every GLAM in the world seems O.K?
Actually in 99.x% of cases we can get the GLAM name and their deafault language from their IP address…