Good Evening kiwieod.
Looks to me to be a super example of a Boxed WW2 Vintage OSS Bushmaster Firing Device.Nice find, and good to see the bi-lingual instruction sheet.
I presume that you have Dr Brunner's excellent book, so I would also reccomend The Plumber's Kitchen - The secret story of American spy weapons by Donald B. McLean 1976 ISBN 13:9780879472030.
There is also the Summary Technical report of Division 19. National Defence Research Committee Volume 1 - Miscellaneous Weapons that you should be able to find online. This deals with the development of the three devices that were developed in the Bushmaster programme namely Firing Device, Single shot, Delay Firing Device, Auto Weapons Type, and Firing Device, Auto Weapons, Pull Type.
Also worth a look - Shows the Firing Device attached to a OSS Supressed M3 Grease Gun. About 8 Minutes in.
https:
www.youtube.com/watch?v=-hNLrDbw8nc
I have never seen a single shot example, but I understand it was a .45ACP tube for the barrel, with threaded end cap connected to a modified Time Pencil used for the firing pin. A spring clip was fitted to allow the device to be attached to bushes accordingly.
Delay Firing Device, Auto Weapons Type used the same trigger clamp as your example, substituting the Pull Firing Device with a Time Pencil of appropriate delay.
Hope this helps.
Cheers
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