In the two photos, just above the points pivot shaft with the retaining clip, there's a hole in the breaker plate that holds a small eccentric screw. Your screw is missing. There is a screwdriver slot in the top of that eccentric screw so that when you turn the screw it opens and closes the points gap. It's helpful for fine adjustment but you can get by without it.
I've refurbished quite a few of these distributors and have replaced the top of the breaker plate with a later breaker plate. That allows you to use the later points used in the 1/75 through 9/77 2F distributors. It's the same breaker plate used in the later non-US F distributors. I may have one more set of parts to do this easy conversion, I'll take a look this morning. For details, check my post from several years ago:
This morning I completed the upgrade and refurbishment of a '68 and earlier F engine distributor using new NipponDenso parts. The starting point was Part Number 19100-60042. My primary goal was to identify and install a non-Land Cruiser Toyota vacuum advancer with a similar vacuum advance curve...
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