Is this old chain of a different type?
Different chains, including modern ones, have all sorts of patterns or markings on the tips of the pins. On some there's some level of intentionality to it as a shift aid. There are no bike chains where all the links are screwed together. (There are some half-link styles where the pin screws in place, but that's a tangent.)

The pictured chain is an older bushing-type chain, which was the norm until bushingless chains took their place. 

From the look of the cranks/rings/guard the bike is a bike-boom era 10 or 12 speed (as in 2 front chainrings and either 5 or 6 rear cogs). If so, chains specific to such drivetrains, which are labelled 5/6 speed usually, are still made and available. You could order one, but many shops don't carry them, instead choosing to use more modern 8-speed chain for replacements on such bikes, which works perfectly.