These shirts have a front zipper and zipper cuffs, double reinforcements all the way around the sleeves at the elbows, and a couple of really cool "belt loops" on each side. The "belt loops have a snap at one end that let them ride flat against the shirt, or they can be lowered to form a sort of "hanging loop". I'm not sure how they were used in the field, but I'm sure I'll find some great use for this feature. Oh yes, and they have a small "cell phone" pocket on the left sleeve. There does not appear to be any date stamps on the shirts, but they are the M83 uniform style, so I would assume that these shirts fall somewhere between 1983 and 1993.
Here are a couple of pictures showing the "belt loops" in the upper and lower positions:
Here's a little history on the Swiss "Alpenflage" camo.
Officially this camo pattern is known as 1955 Swiss Liebermuster, but is better known as "Alpenflage" by collectors. This pattern was based on the German Waffen-SS-Liebermuster camo pattern that saw very limited use at the end of WW2 in Germany (1945). The colors were inspired by the mid 1950's Czechoslovakian Liebermuster camo patern. The Swiss Alpenflage camo was officially adopted in 1957 and was discontinued in 1993 and replaced with a new camo that is nearly the same pattern, but based on woodland colors, without the white flecks.
The Alpenflage pattern uniforms are still in use by the Swiss Reserve Army, while the regular army uses the new woodland style camo uniforms.
Here are a few "historic" pictures of these uniforms in use: