Here are pictures of 2 Mk1's and 2 Mk 2 Premier lamps.
No 1 (L-R) shows a single top pin with the two notches where the 2 horizontal steadying pins would be.
No 2 shows an earlier version with just one thin horizontal pin left
No 3 shows a Mk 2 with the standard blade fitting
No 4 shows a Mk 2 with (standard) but elongated blade.
Over a period there were small variations to all the models, Name style, water lid shape, water adjust lever shape, etc,
Apart from the ecological concerns they give off a very nice soft diffused light for caving. I used them on both the 1964 and '67 Pearce Berger expeditions (11 days continuous underground) and the Pyrenean Ice caves as well as the UK with very little trouble apart from the 'odd' explosion or 3