I've got a very good and detailed answer from Ekkehard Pfau (http://home.arcor.de/pfaue/tromsa/tromsa.htm ) :
This Kit is a "Kombination 711/4"
The wrap is "Blau Schiefer"
The year of manufacture is between 1960 and 1966.
Catalogue-Price was DM 784,00 in the mid 60's
TROMSA used two types of wood. The shells of snare, toms and floortoms are made of poplar, with beech reinforcement rings. The bassdrum shells are made of beech, with beech reinforcement rings.
The bassdrum-hoops are not the original ones. Normally, they are white laquered and have an inlay of the same wrap
or are comletely wrapped, with white laquer stripes on the edges.
The bracket of the bassdrum-cymbal holder is from a later TROMSA series (ca 1975). Normally, it is the same as the brackets of the floortom legs.
The RKB bassdrum head on pedal side seems to be the last remaining original head on this kit. If you take it off and have a careful look at the upper side of its aluminium ring, you may spot a stamped-in date mark. The RKB drumheads were stamped those years, but the marks often hide in oxidation.... If you find one, this is how to decode: "9 65" means "September 1965"
As this set comes from Netherlands, it may have been sold under "Kings" Brand. But it is 100% TROMSA.
Hihat and pedal are from far-east origin, somewhere late 60's to early 70's. With the snare-stand, I am not sure. To me, it seems not to be TROMSA. But it is very similar.