As promised - some thoughts on the No.3 Release Switch. Can't claim to be an expert but I haven't seen much about it written down anywhere.
There seem to be two types of switch body, one with a 5 part hinge and the other with a six part hinge. On the examples I have seen, the 5 part hinge is marked A21 and the 6 part A25 beneath the MD1 stamp on the innner face of the switch. I presume that this is just 2 different manufacturers.
There are also two spring types. The earlier type is just a leaf spring. The later type has a wire coil spring as well. I have seen it suggested that the wire coil makes it a No.3 Mk1, rather than just a release switch, but that seems at odds with the documentary evidence. rather it seems that the springs were added afound 1943/4. As part of an archaeology project I've dug a number of the coil spring type from an Auxiliary Units Operational Base site. This would have been abandoned at the end of 1944 and it is unlikely they would have received any new supplies after June 1944 at the latest. The same source also said the second flat leaf was added with the coil spring when the switches became service standard, though this seems to be wrong. If Millsbomber's box is completely original, then the coil spring is present from May 1943 at least.
The first mention I can find is the British Booby Traps pamphlet which is suggested to be around 1941. This shows a Release switch with six part hinge and a brass snout with a splayed base (are these Mk1 snouts?). It has the 2 leaf spring and no coil. Many extant examples have this spring configuration.
The Oct 1942 dated MD1 leaflet titled Release Switch has an image of a six part hinge switch with snout with the open blackened steel grip (MkIII). It also has a pin that appears to be a solid ring on a split pin as seen in the earlier posting. Possibly it is a split ring on a solid wire pin with a small loop. The National Army Museum have a similar pin in their example (sadly labelled a No.6 switch!)
https://collection.nam.ac.uk/detail.php?acc=1987-03-33-1
The spring type doesn't appear to determine whether there is a 5 or 6 part hinge. Those with the coil spring seem to have one part pins. The design in Millsbomber's box, perhaps best called the "?" pattern seems the most common. There also a "P" type where the ring is to one side of the pin rather than central. Both seem to have the end turned to a blunt point to mke it easier to insert. Millsbomber's looks copper, but dull steel or blackened steel also are found. They were stowed inside the switch with the ring over the square bent brcket in the middle, and the end towards the snout mounting. The snouts must have been individually packed inside the switches as no space anywhere else in the box!
The descriptiom of these as the Switch No.3 Release Mk1 only appears later on. It ppears in the US summary of British switches. I've seen a box lbelled Switches Release from CRC in 10/43, then one from B&P labelled Switches No.3 in 12/43, which seems to date the change in description fairly precisely. I haven't seen any suggestion of Mk2 switch.
The US sheet describes them as Olive Drab, though whole books have been written trying to define that. It appears the switches were painted with British Deep Bronze green. I've never seen any in Service Brown. [Edit] There seem to be a small number in a paler olive green (thanks reccetrooper) see also
http://www.deactivated-guns.co.uk/m...mando-sabotage-tools-equipment/prod_6841.html
Were any produced post war? I've seen a single example with a broad arrow and apparently no MD1 stamp. However, the No.6 switch seems to have replaced this in service, so there would be little need to keep making them. Anyone seen a box dated after 1943?
Happy to be corrected if you think I've got it wrong or have more information to add.