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Essentially their both Hotchkiss weapons (13.2/25mm), I dont believe there was an actual AT version as such and my suspicion is that the gun modelled is a Chinese mod to a captured weapon... I would like to be proved wrong... the gun was capable of ground fire in its original mobile configuration hence the AA/AT gun designation...
The overall length for the gunbreech/barrel etc, should be 90.4"/229.6cm, there are drawings on the internet and a number of sites that give details...