The NAMC’s “Catalog of all Series Matchbox Models” (second edition) list a variation 15-4D characterised as "off-white, decal, four sections that go below bumper {1st casting)". Since no other catalogue contains details of any casting variations on this model, I suspect this to be a pre-production. Can any member provide clarification/a photograph?
Whilst the AIM's “1-75 Series Regular Wheels” catalogue (second printing, 1983) does not contain any new variations, it does have a note that "The number '137' comes in small or large numbers". We have seen something similar with the crosses on the doors of ambulances. Can any Member provide further details, and is this difference to be found on decals, labels, or both?
Stannard has no variations not already listed by Nick, although Houghton has the Herbie version catalogued as 15c-3 but without further comment.
Leake ("Concise Catalogue of 75 Series Matchbox Toys by Lesney" (4th edition, reprinted 2006)) does not list any new variations on this model.
U.K. Matchbox did not examine the model