Bicycle Mechanics - 70's era BB removal

I'm working on a old frame I found and am having trouble removing one piece of the two piece bottom bracket. I've searched Sheldon Brown and the Park Tool website and cannot find the info. One side came right off b/c it had a standard hex head, but the side shown in the photo has a thin slot tight to the hole for the spindle. BTW - this frame was pretty stripped down already - the cranks were already missing.
Thanks!

It threads out with regular thread(not reverse thread like the other side).If you can get a large adjustable wrench on it,you should be able to unthread it.
It might be in really tight so you may have to work it back and forth until it comes all the way out.
If you don't plan on reusing it you can cut a slot in it with a hacksaw and use a hammer and punch.
Lube "the snot out of it"!

Put some penetrating oil around it then put the frame on top of a bench vise and squeeze the protuding part of the bottom bracket piece to unscrew. Then slowly turn the frame anti-clockwise, if it's a french frame. That's what I did with my french 74 Gitane and it went out well and good without damaging the piece.

+1 to the above. You need a good vise with straight jaws, as you may round the flats otherwise. Failing that setup, use Sheldon's (http://sheldonbrown.com/tooltips/bbcups.html) tool.

also I don't know if this stuff is available where you guys are:
http://www.pbblaster.com/store/moreinfo.cfm?Product_ID=1

but it's A MILLION TIMES BETTER THAN WD-40 and seriously the best penetrating oil I have ever used

I hope this isn't considered spamming, I don't work for that co. or get anything if you try it

it just WORKS, and if you wrench on old bikes, YOU NEED SOMETHING THAT WORKS.

check it out

+1 on penetrating oil. Sheldon's 'big bolt' technique (http://www.sheldonbrown.com/tooltips/bbcups.html)would be a good way to get this cup out.

Otherwise, consider using a hammer and punch/chisel since there might not be enough lip to grip with a wrench or even a vise. There are special tools made to remove this type of cup. Your LBS might have one but since this type of BB is old and obsolete I wouldn't count on it. I would recommend replacing the BB anyway so you don't have much to lose by using a hammer and chisel.

Finally, unless this is a French threaded BB (unlikely given the 4130 sticker...) it is left-handed thread so will unscrew in clockwise direction.

edit - just realized tellyho already linked you to Sheldon's site. RIP Sheldon, we'll all miss you!