These are overprinted every year for the past 40 years ,something new listed mostly from Eastern Europe on
ebay.
Seen a nice Hitler overprinted lot at Regency Stamp Auction at the Milwaukee Stamp Show around 2010 for $1,000 ,it even came with a note from the bike rider who went to each village to get the 20 different sets from the post offices . Problem was nobody ever seen this overprint in 50 years ......got no bidders .