Nice clock - a "time-of-flight" clock I believe, used in Lancs and other heavy bombers.
Here is mine ( with yours on the screen in the background )
" When you're chewing on life's gristle, don't grumble, give a whistle "
These were emergency 'bail out' bottle or emergency bottle for use in moving in a stricken aircraft to deal with structural or fire emergencies at altitude untethered from the main aircraft O2 supply system. Very short duration 5 mins or so. These are missing the webbing carry sleeve and strap. Likely not used in a mossie, more typically heavy bombers. You don't have a good picture of the decal so hard to say what it is. The ones I've had do not have a decal in that location - could be there for any reason by anyone over the last 70 years.
Thanks for all the info guys, I thought they may have been used in Mosquitos as I believe they were owned by a member of 409 squadron flying from Carpiquet. The decal looks like a globe and I can make out the word Phoenix in it.