Thanks for the headstamp drawing-and thanks to johnnyc for the box label.
Hooke, your headstamp is very interesting because I think it was made by a very different company than the 2013 headstamp illustrated below which is from johnnyc's box. Notice the difference in the "K", the "E" and the "9". The spacing of the letters is also very different.
I think the 2013 headstamp looks like it was made by MFS (RUAG Hungary).
The "K" on the "12" round Hooke pictures is really different than any that come to my mind. Does anyone have any idea whose it is???
Since the MKE request for bids was dated April 2011, I'd be surprised if they got the contract awarded in less than a year so production deliveries were likely in 2013, but perhaps in 2012.
Either the 2012 headstamp was from a previous contract, or perhaps MKE awarded a contract to more than one bidder and both cases were deliveries against this contract.
I suspect the second alternative is correct since I have an MKE 05 with a red pa which is confirmed to be made by MFS, and a MKE 12 which has the same basic letter style as the MKE 05 and MKE 13 (except the "M" is very different). All three of these rounds have the same brass bullet!
There is another alternative. The primer crimps between Hooke's 2012 headstamp and both my 2013 hst and the 2005. The 2005 I have was reported to be completely loaded by MFS for MKE. Perhaps this is true and my 2013 load was also loaded by MFS for MKE while Hooke's 2012 was loaded by MKE (with the smaller primer crimps) from the cases supplied on the 2011 contract!
Other thoughts appreciated!