<expect any similar scheme would work....but I would exhort you
 <not to use the 'x' thing, because it will create difficulties in a
 <computer database in which the numbers will need to be entirely numeric
 <for sorting purposes.

Regarding the use of x or other characters in Accession numbers.  It depends
on your set up, but if you have a choice the Accession number field should be
set as a character field, not numeric.  Characters include numbers and
letters.  The only time that numeric fields are necessary are when you need
to calculate-total value for insurance purposes, etc.  In a character field
numbers and letters can happily coexist and be sorted.

Frank Thomson
Curator
Asheville Art Museum