From the width of the vision-flap holes, it does indeed look like a MkIV. The early advertising pic looked like a MkV with a MkIV right sponson (possible composite). Perhaps they have thoughts of adding a V if the IV is a sales success?
Going by these photos, the end result should be impressive.
To quote from their F/B page " we already have a substantial order book for this kit, it is certainly different to the WWII tanks we have produced previoulsy, but proving very popular " so things are going well for them so far with this one.
Paul
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The finest stories of the Great War are those that will never be told.