Cannot say for sure but those were my go-to primers over 30 years ago in 20 gauge reloads. Have suspicions that the modern day Cheddite is an offspring of same. Both were/are products of France. Worked fine when I used them.
If Primmers would be more available - I would keep them as an antique -worked great when I started reloading
Rio Primers, never failed to fire, and burned slow burning powder very good. GB.......................................................DLS