Classical Male Nude – Elegant 18th Century Engraving

Elegant antique engraving of a muscular standing male nude, seen from behind.  The engraving dates to either the late 18th or early 19th Century.
There is an annotation lower left which appears to read: J.F. Bolk (?) ad vivum del gbr. 1791 et fc zbr 1792.  (See image below)
There is some light spotting and discoloration as shown.  Purchased in the Czech Republic.

On old wove paper with a watermark H.D. in a symbol featuring three circles and a cross.

Dimensions: 19 x 24 cm (full sheet)
Platemark: 15 x 19 cm