Valira Torrent - bulletin of the Andorran Philatelic Study Circle. Issue 41, p10 (Apr 1995).
It would seem that for each new issue of stamps, the Spanish Administration makes at least three special first-day handstamps. One is reserved for servicing FDCs for subscription clients to the Philatelic Service in Madrid; one is sent with the majority of the stamps to Andorra la Vella; whilst the other is kept as a spare in Madrid (or for possible use on the Philatelic Counter in Madrid?) Normally these handstamps are identical or almost identical, and may show only very minor differences.
However, in the case of the Nature stamp (29pta Hygrophorus gliocyclus mushroom) issued on the 27th September 1994, there is a striking difference in one particular letter of the word "CIRCULACIÓ". The handstamp used in Andorra la Vella has the correct acute accent on the "Ó" of "CIRCULACIÓ", but many of those distributed by the Philatelic Service in Madrid have the incorrect grave accent on the "Ò" of "CIRCULACIÒ" (see illustration above). The third example of this handstamp has also been seen and was used in Madrid, but this has the correct acute accent.
Mushroom Stamps: Countries A http://www.mv.com/ipusers/dhabolt/dad/mushroom/puffball/puffball5/stampsa.html