Thanks you, Qrt.S for your insight.
I now have no doubt about the second spoon provenance (1822, Grönwall), but I am still a bit puzzled by the middle mark, and will check it under the microscope. It is no doubt plated, and has obvious wear showing white metal underneath. I will test what metal it is when the testing kit arrives. Was it required to put date mark on the plated items made of "nickel silver"? I need to look more closely at plated items next time.
As for the first spoon, and the alleged date mark, it could be a two digit mark (X?) only if it is inverted comparing to other marks, and than it could refer to any number of years. Than, if GM refers to Gustaf Möllenborg (1823-1851, https://sv.wikipedia.org/wiki/Gustaf_M%C3%B6llenborg
), X? can refer to X3 or 1828. I could only find two photographs showing his marks. On both, date letters are stamped in a rectangle, and name mark does not have dots between letters and after letter M. However, if the date mark is not inverted, it could only point to 1710 (single "X"), before the official Swedish control mark was introduced, leaving the other mark unidentified, and making me even more confused.