In the spring of 1918 the R.F.K. was introduced and by the end of the war over 3 million masks had been produced. The most significant difference from the C.E.M. is the 6 point banding and the green filter.
Warning: Undefined array key "HTTPS" in /homepages/16/d614955160/htdocs/test/_data/templates_c/3esb8n^50674ff79789aa27cd5b62ce30bf14d5437d8513_0.file.http_scheme.tpl.php on line 26