Of course you may put the 3 boxes into Histograms. If you want, here comes some additional info:
Both models were designed by Sir Giles Gilbert Scott. The larger, taller box is the K2 and first appeared in 1926. It weighed one-and-a-quarter tons; because of its weight it was rarely erected outside London. The smaller box is the K6 which first appeared in 1936 and was half a ton lighter. This can be distinguished by its windows; the K6 has two small panels either side of a large central panel; whereas the panels on the K2 are all of a uniform size. Another unusual feature of the K2 is the crown; it contains vent holes for ventilation! The crown on the K6 is moulded.