Hi John and all
Pic is e.g. at:
From style this is one of 57 rebuilt Pz3J/L at MIAG at may/june 1944.(source: Stug 3, backbone of Infantry, Historyfacts) They were all upgraded with bolted on armor
The only confusing point is that it should have MIAG style Zimmerit as seen on other Stugs.
About box mantlet: MIAG used them until the end.
Regards from Vienna
Visit our modelling show "Go Modelling" in Military Museum in Vienna at 10/11th march 2012