Atomic 4 without dipstick hole in block

[boydwest@gmail.com]

I have a 1968 Newport 30 sloop with an Atomic 4.

The location where the dipstick should be (compared to several other Atomic 4 engines I have inspected) is blank. There is no dipstick, no tube, no hole in the block into which a dipstick can be placed, nothing.

Is there more than one Atomic 4 engine dipstick location? If so, where is it? If not, I am curious as to how an engine can survive 46 years without ever getting the oil level checked...