The 5428 was in use by the RAF in 1950, though can't find anything to suggest what type aircraft it may have been fitted to. Certainly not Lancaster, as it was a post war piece of equipment. Possibly it was standard fit to RAF aircraft in production at the time. Here is its predecessor, which came to market in 1947.
radio compass | loop aerial | direction finding | 1947 | 1921 | Flight Archive