I haven't posted anything from my collection for awhile, so here's a little show-and-tell -- the German Marine-Schiffspost Postal Stationery
From June 1897 to 30 April 1899, a 10 Pf postcard overprinted "Nur für Marine-Schiffsposten" (Only for Navy Ship Post) was available for use by crews of German naval vessels. It catalogs in Michel and Einfeldt as MSP P1, and in Borek as MSP 1.
There were three printings of the MSP card -- March 1897, July 1897, and July 1898. The printing date and paper supplier are reflected at the bottom right of each card. In the above example, it's July 1898 and paper supplier "f" as denoted by the "798f". The Germans also used a complex system to denote printing date and how many times the plate had been used by omitting dots from the address lines. In this case, there' a dot missing from the fourth line 30 points from the left, indicating the July 1898 printing date and the first run with this plate.
At the time, the cancellers carried by German naval vessels were of an identical design, but each with a unique MSP number. A ship could carry the same canceller (and therefore the same MSP number) for years or for only a single voyage. However, there are excellent resources available that list the dates and locations of each ship/canceller, allowing a collector to pinpoint the ship and its location simply by the cancel. For example...
This MSP card carries an MSP No. 16 cancel dated 21 March 1898. At that time, No. 16 was assigned to the training ship SMS Charlotte which, on 21 March, was in Dartmouth, England.
This MSP card carries an MSP No. 40 cancel dated 28 December 1897. At that time, No. 40 was assigned to the cruiser SMS Deutschland, which was off Gibraltar en route to the East Asia Squadron.
This MSP card is a rare one. For the first several months in which the MSP cards were available, the fleet did not yet have the circular cancellers, so postal clerks onboard resorted to handwritten cancels. This cancel states "Von der Marine-Schiffspost Nr. 10 ungestempelt beim Marine-Postbüro eingegangen. 26/8 8 V" (received uncancelled by the Navy Post Office of MSP No. 10). At that time, No. 10 was assigned to the cruiser SMS Condor, which was in Dar-es-Salaam, German East Africa from 29 Jun-11 Sep 1897.
Prior to arriving at the final design of the MSP card, several essays
were produced testing different fonts and different placements of the overprint. There are 24 known essay designs. I've managed to find 11 of those.