So why would I in any way doubt that letter? Well, I didn't really, but there are facts in that letter which turned out to be not true, so it may well have been written with a little poetic licence. A la française, shall we say. Seeing that the letter mentioned stamps engraved by father Gaston for which other information was available as well (other engravers, other printers), I just wanted to know more before entering the information in my database.
So I was very happy to bump into the French philatelic magazine 'Le Philatéliste' of December 1941 which includes an obituary on Gaston. The obituary gives quite detailed information on Gaston's work, so I think we may from now on safely presume the following:
Gaston engraved the three recess-printed designs of the 1928 Orval issue for Belgium: that is to say: the Orval Abbey, Duchess Mathilde, and the Cistercian monk. He also engraved the top value of the 1932 Mercier issue, again for Belgium. A third Belgian stamp he engraved was the 1f75 value depicting St Gudule Cathedral, of the 1928 Anti TB Fund set, a rather stunning stamp, I think.
For France, as we know, he engraved the 1936 air stamp and the 1939 Strasbourg stamp. But the obituary also mentioned a French stamp depicting the Garabit Viaduct. Now, the only French stamp (to my knowledge) depicting this viaduct dates from the 1950s and is engraved by Pierre Munier, so that couldn't be it. Digging a little deeper, I found a set of parcel post stamps issued in 1941, which included a design with that viaduct on. Recess-printed by the Institut de Gravure (for whom Gaston worked), so that fitted the bill and, being now the proud owner, the stamp does indeed mention Gaston as the engraver.
The set comprises four designs, three of which were engraved by Gaston. The fourth design was engraved by Achillle Ouvré.
Moving on to Africa we now know Gaston engraved the 15c definitive of the 1931 Belgian Congo definitive set. The obituary only mentions the country's name but a picture of this 15c stamp was included. It could well be that Gaston engraved more if not all values from this set, but there's no information on that.
For Senegal, Gaston engraved the 'Senegalese Girl' design for the 1935 definitive set.
Gaston was also involved in the Pétain omnibus series which was to appear after his death, in 1942. He engraved the stamps for four French colonies: Ivory Coast, Madagascar, Niger and Senegal. I checked these stamps and found that on all stamps the name of Georges-Leo Degorce is also mentioned. In fact, all sets include his name next to another engraver's name. Because of that I'm assuming that Degorce engraved Pétain's profile, which is identical on each and every issue, with the other engravers (among whom Gaston) engraving the vignette.
Finally, the obituary cleared up the matter of Gaston's passing. Pierre's letter mentions he died a few days after Hitler arrived in Paris, which was in June 1940. However, this is not true. Gaston was involved in the project of engraving the souvenir stamps for the 1941 philatelic exhibition in Paris. He engraved the Ecole Militaire stamp which I showed last time. The project was thought up somewhere in July 1941 and the exhibition was held at the end of the year, so Gaston must have passed away in the second half of 1941. The obituary does not mention a date but the magazine is dated 1 December 1941, so I presume Gaston passed away in November.
This would, finally, clear up yet another matter: that of Pierre's signature appearing under Gaston's engraved die proof of that Ecole Militaire stamp. Gaston must have passed away before being able to sign these die proofs which, I presume, were made available at the exhibition. All the other engravers signed theirs, so son Pierre must have stepped in for this particular one. The magazine did state that this stamp was Gaston's final work.
A lovely farewell to what all described was a modest, gentle man.