And now, a day 5 years in the making!
First, a little background. During WWII, the Germans recruited volunteers from the conquered countries to serve on the Eastern Front. Those from the Flanders region were formed into Flemish units which bore many formal names, but are commonly referred to as the Flemish Legion.
Beginning in 1941, several series of private donation stamps were issued by Belgian support organizations for the benefit of the Flemish Legion. These were not valid postage, but were attached to mail for propaganda and recruitment purposes.
The Emperor/Empress sheetlets were available beginning 9 August 1943. Approximately 30,000 sets were printed, though most are of the perforated variety. I couldn't find a reference for how many imperforate sheetlets were printed, but if the catalog price is any indication, the number is extremely small.
On today's philatelic market, the imperforate Emperor/Empress sheetlets are the rarest of the Flemish Legion sheetlet sets, and it's taken me over 5 years to acquire them. I let a set get by me in 2007, and this is the first set I had seen at auction since then. I went so far as to have a dedicated stash of funds set aside waiting for the day this set appeared again. And lo and behold, last week the elusive Emperors (and Empress) poked their heads out of deep hibernation...
Note that this set bears matching numbers, which would seem to indicate the set was originally purchased by a collector and has remained as a set from day 1. It's also an especially low number (#000002), so he/she must have been near the front of the line on 9 August 1943! Should have pushed the other guy out of the way and purchased #000001!