I've owned my car since 1976, drove it regularly for 4 yrs or so before I parked it in 1980, and always believed that stuff was 'restoration graffiti', until JohnZ explained to me once a couple of years ago what they meant and they were 'really put on the cars by Fisher body'.. so I went with a bright light and looked .. and. VOILA.... there they were, and after I took my brake booster off the firewall, I found a 'second T' behind some of the components under the Trim tag.. (all on the driver's side).. I never found any on the passenger side, even after removing the heater housing.