@txlabman tells me via a message that the oiler isn't original. Though I have to agree with what he told me, it does look pretty good sitting on the engine :-)
I have seen another B38 with the oil hole threaded for an oiler. If it’s threaded, it likely had the oiler installed from the get-go for extended run times with the display. Like the book says, some had it, but likely most didn’t.