Stupa's official designation was Sonderkraftfahrzeug 166 - Sturmgeschutz IV mit 15cm StuH 43 (special military vehicle 166 assault gun IV with 15cm assault howitzer 43).

Tarpin wrapped around empty wheel slot made from tissue paper + water + Elmer's Glue, painted with thinner + Testor's Forest Green enamel paint. Panzertruppen (armored crews) practice was to hang utility items (tools, bucket, helmets, etc.) on external hull to alleviate cramp conditions inside compartment. Panzer page - www.wargamer.com/Hosted/Panzer/panzerpage.html

Inset : Third official version mounted sIG33 howitzer within enclosed fighting compartment of Panzer III chassis, hence all-around protection from enemy light-caliber fire, gun transverse by turning entire vehicle. Previous sIG-33/Panzer III version was field modified with open fighting compartment. German designation is Sturminfanteriegeschutz 33B (Assault Infantry Self-Propelled Gun 33B).