We only know 67 pieces from or to the S.I.M.’slabor camps and auxiliary prisons, but, despite having them listed in our catalog, we cannot guarantee that all of them still exist. We don’t know if those extracted from books or articles (045, 061, 064, 065 and 066) are still preserved or if they have been lost. On the contrary, we don’t know how many pieces related with the S.I.M. do exist in private collections, in the hands of relatives of former prisoners, or forgotten anywhere else. We can divide the probable undetected pieces in collections in two groups:

a) Those whose owners know are S.I.M. related.
b) Those which are in the collections and their owners don’t know they were sent from or to S.I.M. prisons or labor camps.

As it is obvious seeing many of the pieces in the catalog, it is usually difficult to discover if they are S.I.M. postcards or covers, unless we read its content, we take care inspecting the addresses, or we do some research about the individuals mentioned on them.

Francesc Badia, who has most deeply studied the history of the S.I.M. labor camps, wrote that “Examples of correspondence coming from inmates of the Catalan labor camps are scarce, and for this reason they are very appreciated by specialised collectors” (145). About incoming mail to the camps he said “ever rarer than the referred postcards, are those pieces of postal history addressed to prisoners in the labor camps and received by them. I’ve neve seen one. The bad living conditions of the prisoners, and the fatigues suffered until their liberation, made very difficult that documents of such nature could be preserved” (146).

Out of the 67 pieces we could list in this catalog, only 7 are incoming mail effectively delivered to the addressees, and there are four other pieces that were returned to the senders for several reasons.

The scarcity of this type of postal history is due to the fact that the S.I.M. penitentiary system lasted only a few months, from April 1938 to early February 1939. Actaually, the last registered postcard is dated on January 5, 1939, and we think that the mail to or from the camps and prisons was disrupted in mid January 1939, as the rapid advance of the war front forced the camps to continuously move towards the French border, until all groups crossed it. It may have been very difficult, under these conditions, to organize the mail system. Other factors that make this type of mail so scarce is that inmates, in most of the camps and prisons, had a limited ammount of mail allowed to be sent each month, usually only two postcards. And finaly, the number of prisoners in the S.I.M. camps and prisons was of a few thousands, most of them war prisoners without any chance of communication with their families in the Nationalist Spain, as there was no postal communication with that territory from the Spanish Republic.