Many thanks for your thorough and most informative reply! I recently acquired his BD tunic and beret, the name of original owner remaining unknown at time of purchase. The tunic was adorned with his badges and decorations, among them his Monte Cassino cross, which Andrzejku has since identified as having been issued to sierżant Fiedorowicz. Your ID of the Tobruk badge seals the deal as far as positive ID. As far as rank, the shoulder straps have clear evidence that we was promoted to staff sergeant, and then both chevrons removed and replaced with a star denoting "chorąży", aka warrant officer.
Many thanks again ,