Here is an example of a previously unknown crystal clear British radio strain insulator embossed "PHOENIX" (front eyelet) and "APW 7576 [triangle symbol] 10B7052" {reverse eyelet}. Measures 7 1/4" end to end and approximately 1/2 inch shorter when measured hanging from inside top of upper loop. For a close up of the embossing [id=301254416] and [id=301254663].

This 50+ year old insulator was made by the British Heat Resistant Corp at the Phoenix Glass factory in England circa January 1958 (marked: "FIA/A W7576, Insulator Glass, QTY 1, H.R.G, Date Packed 1/58" on original box). Seems to indicate W7576 as the style or part number. FIA may be an abbreviation for Fire Industry Association (as they are a government agency that regulates fire codes in England).

The hobby has seen this size strain with similar embossing made exclusively for use by the British Air Ministry during WW2. This example is most likely produced for civilian use.