FF Bradlo is mentioned as the first font to apply traps aesthetically
and the year given is 1995. Since my youth I always admired Metron (1971–1972) by Jiří Rathouský*, a custom job for the Prague Metro. That's why I used traps in Mentone (2008). Below is Metron in use at the "Museum" station, Prague, pic. Wikipedia:
*The authorship of Metron was contested by Prof. Petr Tučný, whose drawings, dated 1967–8 are below:
Source article (in Czech) here
František Štorm digitised Metron, afaik, but does not offer it for sale currently?