Hello there!
This is a brilliant forum so I am hoping someone here can help me.
I'm doing some research on an Air Ministry Stopwatch in my possession. A 6B / 117

Based on what I have already found out, this watch would be circa 1940, however I am trying to discover what differences this may have over other 117 models.

For example I am aware that many Air Ministry models have the King's crown as well as a fairly ornate A.M. on the back, while this watch of mine has no King's crown and a more simplistic A.M. Is this a difference in manufactures or even an indication of the status of the person in receipt of the watch (officer or no, perhaps?)

Additionally the watch face itself is split into a 30 second intervals with a count of up to 15 minutes, however I am aware that other models have a full 360 motion of 60 seconds and up to an hour. Is this indicative of the particular aircraft this watch was used on?

The watch face itself (which sadly has lost its covering) feels rough to the touch, almost like paper. Is this as it should be, or possibly indicative of a potential fake, or some alteration made over the years?

Finally, there is a serial number labelled 2183 / 44 - I am assuming this is individual to every watch, however any particulars on the significance of this number would be appreciated.

Kind regards for any help that can be provided. I am very interested in this watch and I have been struggling to find information for such particular questions elsewhere simply due to my own lack of knowledge and resources. Thank you.