The armoured turret only appearing on the Ausf D, carrying a modified 2cm Flak 38

Sd Kfz 251/17 Ausf D

Since the termination of production for the Sd Kfz 138/1 Ausf M in 1944, troops still needed many 15cm SPGs. It was decided in November 1944 to build it on the Hetzer chassis. Only 30 vehicles were produced, had a crew of four.

Hetzer 15cm sIG 33 (Sfl)

Alternate view of: http://www.ww2incolor.com/german-armor/Bundesarchiv_Bild_183-L04352__Deutschland__R__stungsproduktion__Panzer.html
Labeled as "NbFz Nr.1 (Rheinmetall) in the Krupp factory in 1942" back possibly for repairs but not a lot is fully known. Credit to original owner.