Produced in 1991
Although it is the successor to the Jegan, the Jegan has been in active use as an older model for 30 years. The Heavy Gundam itself has been in use for about 40 years, with minor changes. This can also be said for the Salamis Custom, but in Director Tomino's works, it seems that the Federation Army doesn't update its mobile suits unless absolutely necessary.
In any case, it's a mass-produced mobile suit with no distinctive features, but its face resembles the robots from the Brave series. Even so, the G-Cannon seems to play a more prominent role in the film. The Heavy Gundam seems to be more of a downer...
The MSV Hardygun is still unassembled, but it's still

RGM-109 Heavy Gun [1/100 Face-Only Hero Series] | felicity's Gunpla works