Yes, it is a block plane Stanley P910. It looks about 50+ years old, but shaves very well when the blade is sharpened. It is kinda weird size, substantially larger than usual block planes, but much smaller than the No.3 or 4 planes.
It works really well for certain shape and size of woods not too small or big. For the really small parts of woods, I tend to use a Stanley 102, which also works fine.
But both tightening bolt and nut is worn out, initially I thought. But now I think the nut is OK or better condition than the bolt which looks almost no threads around it.
I have thought about it, and got a few ideas. I have a long bolt with a plastic handle at one end. It came from a defunct work light brackets. The bolt fits tightly to the P910 nut. But it is a lot longer than the original P910 worn out bolt. So I will vise it, and cut it to the same length as the original worn out bolt with a hacksaw, and try it out.
It is fortunate that the nut's thread was not too badly worn. Looking into the hole with a LED light didn't help finding about it due to too much brightness light shed into too small space. But trying the spare bolt with nylon handle gave me some clue, that they might work together, if the bolt is cut to the right length. It will start tightening the blade on the P910 OK hopefully. cheers.