An interesting stem by Btwin, one of the brands of Decathlon, a French sports equipment chainstores.
This is a very solid stem, as if machined from single block of aluminium. That explains its hefth; it weighs 188 grs, the heaviest stem I owned so far.
This model is 80mm; 90mm and 70mm models were also available. Front plate has only 3 screws.
Suitable for 31.8 handlebars. Can be used as 0 or 30 degrees.
A very authentic feature is the stackable spacers. These can be bought separately, several colors were available. You can use 3 different spacers having different length, which corresponds to markers on the top side of the stem, as can be seen on the images.