Black and grey bases

An interesting item came in yesterday, this Jaguar 2.4 with a friction motor. It has plenty of signs of wear but the windows are clear and the motor, whilst weak, does work. What immediately caught my eye was that it has a grey base. Every other one that I've encountered, and all those shown on several other sites like QDT have black bases. 

The text seems to be identical. I am aware of only one other model that can be found with either a black or grey base and that's the Standard Vanguard as an RAF Staff Car.

The 208M model first appeared in 1957 and production will have ceased in 1959, none of the M models being that popular. The last three M models were the 211M Studebaker Golden Hawk, 214M Ford Thunderbird and 216M Austin A40 and these were issued in late 1958 or 1959. All of these that I have seen have had grey bases and all the M models prior to the 208M Jaguar seem to have had only black. From this I am inclined to conclude that the change from black to grey bases would have been made sometime in late 1958 and, therefore, few Jaguars will have this.

The 352 RAF Staff Car was not issued until 1958 so I thought that a black base on this model could be quite scarce too. However, a quick look through Ebay and QDT pages shows that all but one for sale at the moment do have the black base. So that idea doesn't seem right! Maybe the 207 model didn't sell well and there were lots left from earlier years' production which Corgi painted RAF blue and turned into 352 models.

There are at least two variations of the bases for all the early models. That includes the tin base models as well as the solid base versions, whether M models or not, and the early racing cars and Bedford CA vans. The typeface for 'Corgi Toys' and the text itself and the layout you will find are clearly different and I shall have to make a study of these sometime.

For now, though, I would be interested to learn of any other models with both grey and black bases like these. There could clearly be an implication for values.

The 1959 Plymouth Suburban Estate car can be found with either a cream or grey base and the 210 Citroen comes either with or without a rear axle 'bulge' so it seems that the years around 1958-9 were a time of some change at the factory in this particular respect.