The AFF Universe Wiki also has an article on this topic: SM54 'Hand of God' or 'Hog' Infantry Weapon

The Sikfrit Model 54 can be used by either team.

Compared to the other pistols (the ULA's UDP and AIA's EVP), it's slower firing, takes longer to equip, and has less ammo.

But it hits like a truck. It has a high anti-vehicle modifier compared to most other small arms, and can penetrate metal by twice as far.

And if that wasn't enough, it's costs are virtually none. If you've got a free weapon slot in your loadout, a Model 54 is never a bad call.