The following article by Mr. Jerzy Krysiak (Sweden) appeared in the Polish philatelic magazine «FILATELISTYKA», October 1998.  It was originally printed in Polish, and is translated into English by Mr. Richard Wegrzyn, Australia. 

On a commission from the San Marino Post Office Slania engraved three stamps based on paintings by the Italian painter Giovanni Francesco Barbieri (Guercino) of the XVIIc.  The engravings are of  St. Marinus, St. Francis of Assisi and ‘Susan at her bath’.  The stamps are 33.8×43.5 mm., perforated 12 1/4, as well as imperforate. The stamps were printed by hand, less than 20 sets, in one colour but the the engraver painted several of them by hand in various colours.  These are the ones illustrated in the book ‘Czeslaw Slania, his lifework’ published by Count Leonard Bernadotte in 1989, Mainau, Germany.  It is difficult to say why the stamps were not accepted, maybe according to Catholic tastes ‘Susan at her bath’ was a bit too naked? Instead, the San Marino Post Office issued three stamps using offset printing.  Two of them were on similar themes as before, St. Marinus (Mi 887), St. Francis of Assisi (Mi 888), but the third stamp, ‘Susan at her bath’, was replaced by a portrait from the same painter, ‘Return of the Prodigal Son'(Mi 889).  Slania had no hand in the design of these issued stamps.  

(source: Ann Mette Heindorff webpage).