I'm doing a little research on the Orval Abbey in Belgium. Remember I previously showed you an Orval stamp here? Well, today's stamp depicts the origins of that same abbey.
Countess Marthilda of Tuscany had only recently been widowed when she inadvertently dropped her wedding band in a well. Being the devout woman she was, she immediately started praying, and lo and behold, up came a trout from the well who gave her back her ring. "Well," exclaimed the lucky lass, "truly this place is a golden valley!" And so she decided to found an abbey on that very spot in the Val d'Or, which of course was morphed into Orval through the ages. The Orval coat of arms shows the trout rising upards, returning the ring, and that very same well can still be found in the grounds of the abbey.:-)
Adrian
The stamp is the top value of the 1933 Orval Abbey Restoration Fund set, with the other eleven values depicting either photographs of the abbey 
or events from its history, like the restoration of the abbey in the 16th and 17th centuries.
Belgium is well known for its charity stamps. In those early modern days, the majority of its non-definitive stamps had surcharges for various good causes. From 1928 onwards, the Orval Abbey Restoration Fund became one of those good causes. Sets were issued regularly until 1943. The earlier sets were sold as sets and single stamps would not have been available, which probably accounts for their high catalogue price. Our Blue Madonna had a postal value of 10f which must have been a lot in those years of economic hardship, and on top of that you would have had to fork out an extra 40f for the fund! It must have backfird on them, though, for later sets usually didn't have any higher value than 5f!
Nothing to write home about, I know, it's the 3f bistre-brown, issued in 1951 as part of a definitive set depicting King Leopold III. But then I came acros this stamp.
It's an awfully torn copy, I know, but look at the colour. It's bright orange! And it is not mentioned in any of the catalogues I have (Stanley Gibbons and Michel). There is no mention whatsoever of shades and the colour is so bright that I don't think it's a faded or sun-coloured bistre-brown stamp.
The examples shown here are an issue from 1869, designed by H. Hendrickx and engraved on wood by A. Doms. The stamps are printed in letterpress. As you can see, there are two basic designs, which have been used for various values, with additional values being added until 1888. The set is mainly only of interest because of its shades, although there are two varieties to be found on a number of values: CENTIMF for CENTIME and BELGIGUE for BELGIQUE. 
The Dutch set is designed by J. Vürtheim, printed in letterpress and issued in 1869. There are a number of perf varieties to collect and there's the phenomenon of small and large holes. I don't have that many copies so I'm a little out of my depth here, but I think I'm showing you here an example of both small (left) and large (right) holes.