Some more examples.
The "Welcome to British troops" is an earlier card, dating from 1917, no logo but the stamp box suggests the same publisher or printer. The British troops took part in the final Italian campaign which led to the end of the Austro-Hungarian Empire. The same card exists in a French version.
The logo sometimes appears with an extra "series" name, eg FORTUNA, ULTRA. One series, ARS NOVA, was produced by the pochoir process, hand colouring using a number of stencils. This series is dealt with under the GM logo to group it together with other work by the Ars Nova studio.
There is a whole separate section here on the AGM logos which may or may not be related.
GAM 23-2
GAM 605 "calcochromia"
no logo but similar stamp box
