Aw, you guys are such a tease!
It's a Mathieson with the sides ground off to release the lever cap coz the last muppet couldn't drift the pin out (noting the gammy finish on the 2" behind the holes in the sidewalls). Thereafter refitted with a saw type handle (or bits saved from the original infills) when said muppet realised the difficulties of making an infill to replace it.
In short my dear DM, you are the proud owner of a piece of old toot that has been abused to the point of uselessness by a previous owner and then restored by kermit the frog to within an inch of it's life.
In short, if you want a panel plane (very sensible notion indeed) ditch this dog and buy a better one. If you love this casting with all your heart, and I mean heartfelt, deep-seated, marriage levels of commitment, by all means spend between now and christmas getting it to take a shaving (which it will) but understand that it will always be yours because no one in their right mind would buy it for more than you paid for it no matter how much work you do.
This sounds so harsh and I'm cringing as I type, but sometimes if you care for the person you just have to be cruel to their panel plane.
Your best bet would be a nice ceremony in the garden and an acceptance that the bloke who made it would probably have agreed with you that it was time to let it go and search for a better example of his workmanship. I'm sure he would be deeply touched by the value you placed on his output at the bitter end of its worknig life.
