1928 Yugoslavia Airmail Essay

I received the pictured stamp today in a mixed lot and it was marked as being an essay from 1928 for Yugoslavia's first airmail issue. Scott has nothing about this, and I have no other catalogs for Yugoslavia. Does anyone know anything about this stamp? Before I offially add it to my collection or try to sell it, I'd like confirmation of its identity.

Haven't seen one, but it pops up on ebay, and is apparently listed in the Sanabria catalgue of air mail stamps.

My 1959-60 Sanabria Air Post Catalogue lists it under PROOFS, ESSAYS & SPECIMEN:

EAPP 2D Essay, dark red & green on yellow, perf

I don't have the Jugoslavia essay listings from the 1972 Sanabria. (Sanabria spelled it with a J, not a Y. The 1972 partial catalog was the last Sanabria.)

Sanabria does not list a year, nor does it show a value. Several of these essays are listed on ebay, from 1928. I found only one actually sold in Completed Listings. It went for $7.50.

Thank you.

They were printed in sheets of 50.

Here you have unissued stamps of Yugoslavia/SHS
http://www.ephila-stamps.com/index....39&Itemid=56

your stamp is valued there 10 euro and other are 15 and 40 euro depending on colorings of the stamp.

A block of four: