Add some sparkle to your Luxembourg collection with incoming commercial mail from the last 50 years or so. Such mail is scarcer than you might think, partly because meter imprints and stickers have largely supplanted the use of stamps by businesses and at post office counters. This is a sad development for postal history collectors, as I've yet to see a meter sticker that qualifies as artistic or aesthetically pleasing.
But with the likes of Delcampe or Jim Forte's www.Postalhistory.com website (350,000 worldwide covers), you'll still find many beautiful covers from 1960 onward franked with "real" stamps. Even a small collection of these can be quite satisfying.
Here are examples:
Congo
Lubumbashi,
Democratic Republic of Congo
29 July 1967
Airmail to Rodange
2F Fishing Industry
4F Pyrethrum Harvest
10F Cotton Harvest