They were three first day covers from Czechoslovakia. Now as you know, Czechoslovakia made collecting FDCs cool again because the illustrations on the cover are usually hand-engraved as well, and are therefore additional artworks from our beloved stamp engravers! A quick email to my philatelic fountain of knowledge friend in the Czech Republic confirmed what I had already thought: the covers were indeed hand-engraved by the engravers of the stamps on those covers.
And so, first up we have an FDC from 1979, with a stamp from that year's Art series. The engraving of the stamp and on the cover is by Bedrich Housa. The illustration on the cover is that of the Bagpiper, an engraving by Dürer from 1514.
The stamp itself depicts Dürer's 'Dancing peasant couple', also from 1514. They both are stunning engravings.
My next two covers date from 1989, franked with more Dürer stamps from yet another Art series. This time, Milos Ondracek is the master who engraved both stamps and covers.
The illustration on the cover is that of Apollo and Diana, from around 1503. Although both covers are alike, the one is printed in black and the other in deep purple-brown. They each were franked with one of the stamps from the miniature sheetlet.
That sheetlet depicted Dürer's Festival of the Rose Garlands, from 1506. The two stamps show details of the oil painting, but the sheetlet itself has an engraving of the complete painting.
Whilst I haven't seen any FDC with the complete sheetlet on, at least we do have one of those beautiful Mlada Fronta souvenir sheetlets connected to this issue. It is a printing of the complete engraving of the painting, but in monochrome. I'm normally quite a fan of monochrome printings, but I must say in this case I can't really choose between the two. The original being a rather brightly coloured oil painting, I do think the multi-coloured engraving does the original work justice. See for yourself, and remember you can click on all images to see them blown up!
Anyways, all these new items make me rethink my dream of building an engravers collection of Dürer material once again, so maybe I should just give it a go someday...