Differences beetween Sumida model P and type 91

When one look at photos about the Sumida model P, one can see some minor differences betwwen models. It seems that only three were built (see Sumida model P history) but there are two versions. One without rear fenders and without ball mounts and one with rear fenders and two ball mounts. The ball mounts were not symetrical on each sides. On the left side, there are three gun ports, the first beeing a ball mount. On the right side, there are three gun ports, the second beeing a ball mount. The Sumida went to the Navy only (IJN). The Sumida type 91 which went to the Army only, in fact to the railcorps, was a modification of the model P only in terms of adaptations to the rails. The Sumida type 91 was built on the basis of the model without rear fenders and no ball mounts, it can also be recognized by the roadwheels attachments on the sides. Below is a photo in Tsingtao where one can see the two models together