There is very few good literature on the Putilov-Garford armoured trucks around. The best monograph certainly is Maxim Kolomiets’ “Russky Garford” (Russian language). I also did an in-depth article with new findings on the Freikorps versions in Militärfahrzeug magazine N°87 (German language) in winter 2023. As for the latter I was in contact with CSM to make a correct model. As much as I admire CSM’s approach to WW1 armoured cars, the cooperation came to an abrupt end when it became clear that the plastic kit of the Freikorps’ two versions suffered from the fact that these were naval Garfords rather than army Garfords and additionally needed extensive Germanisation - with details provided by me yet only partially taken over by CSM (and my free help ignored in the acknowledgements). The two batches of Garfords were purchased on a completely different basis that led to 8 production batches among only 14 naval vehicles completed! Some chassis were 670mm shorter than the army batch, others 715mm longer (this is not only linked to an increased payload only but also for chassis intended for specialised trucks rather than the cargo versions and gathered to fulfil the Russian order in a tight timeframe)! That many versions could of course not be covered by CSM in kit form so a number of resin upgrade parts were produced to cope with the many many differences. In the end CSM made a commercially understandable decision in producing the 1915 army model and basing the other variants (including the naval ones) onto that unchanged chassis. From the fan’s point of view many versions need comprehensive conversion (many covered by CSM resin updates doubling the price of the kit) to look fully original.
PS: There seems to have been a version with the roof openings closed on the post-war era, but due to the absence of good top views there is a wide margin of error here and it needs further research.