I might be wrong about the HF1300 being derived from the GEC tweeter, because here in post No. 3 it says that the GEC tweeter was a rebranded Celestion HF1300

http://www.diyaudio.com/forums/full-...-tweeters.html

The poster says that he worked at GEC Hirst Research Labs where the GEC Metal Cone speaker was developed. Coincidentally, I worked a few miles from there, at GEC Marconi, but that was from the 80's to about 2004.