Not exactly rare Tokiem did manufacture coin op pumps right up to the Explorer series , uh 1960's . Heck, I used to keep my Corvairs fed with Genuine East Coast Gasoline happy with them! East Coast gasoline , a brand BOTH Carolina traveler and I remember had them at all their "Quality " locations , ahem..........
Now I dunno bout an earlier Tokiem 300, they were made from 1954-1960 or so . I would imagine the same mechanism used in the Explorer pumps could work for the 300's too. The Explorers had a switch that allowed one to feed quarters and dollar bills, well , later ones did and had a buzzer to tell the customer the pump was on when it was dispensing gasoline .
Rare, uh doubt it . UN- Common , uh yes . Hey scrounge up a coin box and put it in yer den, people will wonder about ya !
Ed Shaver