Gary raises a very valid point regarding the absence of Cartridge and Calibre. It was something I was aware of when looking through AP.1661E as I had to check both 1" and 1.5" Cartridges. The signals as described in AP.1661 E are "Cartridges, Signal, 1 1/2 in., Double Star, Mk. 2T - which is what you would expect to find stencilled on the container.
The item shown on Gary's image is described as "Signal Double Star Mk1" As there is no mention of a "L" number, one presumes it was introduced before 1954. Also, in small print on both parts of the image is "Land Service". There is no trace of the store in either (my) AP.1661E or RAOS Vol. 4 Pam 18. Pyrotechnics.
The RAF did have a "Signal, Distress, Two-Star, Red, Mk 4" for use at sea and was contained in K-type (fighter) dinghy pack.
TimG