The model number stamped into the cap ring is a dating feature, though a blunter one than is often assumed. The “146” stamp was used until roughly the end of the 1990s; it is therefore no evidence whatever of manufacture in the 1970s, it merely puts an upper bound on the period. When further models such as the 147 and the 166 came along during the 1990s, marking by number was dropped. The same applies to the Solitaire variants, which were first supplied with the number in the ring and later without it.
A Meisterstück 146 or a Solitaire of that size with the number stamped therefore dates from before this marking was phased out, a pen without the stamp from after it. For a closer placing, other features have to be brought in: the form of clip and cap ring, the engraving and alloy of the nib, the design of the ink window, the shape of the feed and the material of the body. Combined with dated catalogue illustrations, this will usually narrow things down to a window of a few years.