The earliest stamp I have seen that was engraved by Maciej Kopecki is this one from 1974 featuring a sixteenth century woodcut
of a hunter.

Poland 1974, Folklore SG 2338 Scott 2071
His career started at a time when engraved
stamps were being produced less and less but Poland had a group
of excellent engravers to mentor him.
Kopecki's output has not been large but over the years he has produced better and better work, such as this portrait
of Queen Rycheza from 1988.

"Where is this leading?" you may ask. Well today's mail brought another Kopecki gem and I can't wait to share it.
By 2013, Kopecki had become PWPW's chief artist and when they decided to produce a miniature sheet to celebrate the 900th anniversary
of the Chronicle
of Gallus Anonymus, the first written version
of Polish history, Kopecki engraved it himself. It was designed by Agnieszka Sancewicz.
The result was voted the best intaglio stamp for 2013 at the Conference
of Government Postage Stamp Printers' Association (GPSPA) in Beijing. Here it is.

Close-up
of the stamp portion:

If anyone can give me SG and Scott numbers for this, I'd be grateful.