[quote=@Rhona W]
Though, it's still very much a work in progress! 

[/quote]

Okay, looking through the lore, post heavenfall, North Korean tanks are in excess, Vietnam's industry is on the rise, and Isreal had war looming on the horizon.

So basically I'm figuring some interested parties bankrolled some mercs getting [url=https://tanks-encyclopedia.com/coldwar/north_korea/68-type-68/]ex-DPRK Type 68s[/url] up to Vietnam's T-54M3 standards (or Ti-67/Tiran-5Sh) and shipping them to the middle-east/etc en-masse.

Vietnam would've probably still upgraded their 9M14s and decided to slap some missile-racks to the turret-sides along the way, similar to the Peruvian Leon-1 tanks. And the expedited nature of this upgrade would imply that rather than actually rebarrelling the T-55s, they just bored them out to 105mm (smooth). I'd probably throw in some indig-tech of maybe 100/105mm rocket-boosted HEAT-FS. Maybe slap a surplus Ukranian T-64 commander's cupola in with it.

OTOH, a lot of 100mm armed versions would still exist solely for their superior ability to provide HE-frag rounds for infantry support out to 12 km instead of 8km.
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Counterpoint: [url=https://tanks-encyclopedia.com/modern/ukraine/t-62ag-and-t-62agm/]T-62AG-120[/url] made from surplus Chon'ma tanks driven by CAA mercs to assist the Isreali army.