If Nitske's book is to be trusted it might be a 170ST or, unwittingly, a 170STD The regular 170 had vertical louvers on the hood while the S models had 2 horizontal bars.

E wasn't used to indicate FI until the 58 or 59 220SE even though it was already used in the 300SL, the 300Sc and 300d. For that matter, T was first used to indicate [what we call] wagons with the 123. It's a wonder the W186 and W189 weren't badged as S's when they are more S than any subsequent S can aspire to be.

That 170 needs a rack.

Sixto
87 300D