Gillette Techs Made in England (no data)

I’ve recently acquired 2 English made Techs. While one has Gillette embossed on top of the head, it has no other markings. The other has nothing indicating Gillette. In fact it only states Made in England on the base plate, as well as having a letter on the right and a number on the left (on the triangle portion of the underside of the base plate). Also note how that’s backwards from the US which would have the Letter on the left and number on the right.
Does anyone know of a way I can determine the age of these two? The only ID data I can find all relates to the US models.