In ten years, I have never seen such a post topic, well done
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A stamps value generally lies with it's scarcity
not by it's designer, but certainly the designer can add
to the value when married to the rarity.
Slania would appear the most collected engraver, due to his
extraordinary skill.
I have known a collector who sought all Jennifer Toombs work
(generally the Pacific region)
Personally I like the work of the chaps in the early twentieth century, art nouveau and art deco, and have my favourites,
Being a sixties hippie, naturally the dreamy girls of
Alfons Mucha were plastered over our bedroom walls, and the
connection followed over into stamps.
I have not collected as a dedicated theme, but have often
considered that, I do certainly isolate examples of
designers in my virtual stamp image database.
I particularly like, Italy=Corrado Mezzana, GB= Edmund Dulac
GB= the lettering and value tablets of Eric Gill,
everyone who collects would immediately recognise
the brilliant designs of Willi Dachauer in his Austrian
"ears of corn" and "hammer and pincers" set.
The extensive resume of Eugene Mouchon is a ripper,
and the entire catalogue of the American Banknote issues
are /would be a fascinating collection.
It is difficult to get literature that addresses
stamp design , William Finlay is the best I have come across.
Good luck with your journey, Slania would be a great start, but
seek out other stamps that appeal, and check the designers,
you will probably need old fashioned stamp catalogues to
reveal those.
Part of Eugene Mouchon's resume: