I always assumed it was the date they started. But according to old versions of their site it says they were founded in 71.
This is the only information I could find on their old site about 1970:
"In 1970 Bob was doing promotional work for several R/C manufacture's including Jerobee Industries, (manufacturers of the first 1/12 scale R/C car). It was the need for accessories for the Jerobee that gave BoLINK it's start. The first 2 products for BoLINK were a Brake and an Electric Starter Motor for the .049 powered car. They were designed by Bob Emott (of slot racing fame) and sent to BoLINK to produce. Then a larger fuel tank was added to the line. The rest is history."
BoLink also bought Champion Slot Racing Products in 1970.
The 3/70 could be a production number but it seems more logical to be a date.
This "Hot-Rodz!" line consisted of the
C-Dan here, another car called
Coop, and a truck called
Truk-R. I'd venture to say that this was one of their most unknown lines. There isn't much info on them out there which leads me to believe they weren't around long.
They all used the same box and it was most likely denoted somewhere on it which one was inside.
They're more or less just Diggers with hot rod bodies, and a wheelie bar possibly from BoLink's Little Red Wagon.