Circlip, thats a tower from a type2D, secondly, the lamp is standard fitment to all type2s post 1933 and it's NOT a coachlamp, it is known as a 'Schtandarte Lampe'. I really thought a chap of your calibre would have known that!!
A bit of naval history here:
On night time operations, an increasing number of U-Boat sailors were being lost overboard when, after sinking oil tankers, the decks became oil soaked due to cargo spillage and they were losing their footing on the slippery decks.
This was brought to the attention of the marine design teams back home and a brilliant engineer by the name of 'Heinrch Schtandart' designed these lamps to pop up when the boat surfaced, thus lighting up the decks and ensuring sailors stayed safely aboard and after approval, they began fitting them to the U-boat Type2D's
After the war, the Allies commandeered all the u-boat drawings and a sharp eyed 'techy' spotted this useful feature. Due to accute shortages and a lack of industry back home, thousands of these 'Lampen' were shipped from Germany as war reparations and converted to domestic use to become known as 'standard lamps' . That is so, so, typical of the British, got to muck about with the name!
The Chinese, ever an eye to business, nicked the whole idea, copied it and now supply B&Q with millions of them.
In one respect you are correct, when fitted in the garden, we call them 'coachlamps', when indoors, 'standard lamps' but when fitted to a U-Boat, it is always called a 'Shtandarte Lampe'.
I have to say, this was my prototype boat but I no longer fit them to the kits as there were insurmountable problems encountered with the retract mechanics and if they stuck in the upright position, would spoil the hydrodynamics of the vessel.
I try to be a stickler for accuracy you know!