How to remove Shimano MF-HG20 freewheel?
 

I offered to clean up a bike for a friend, and encountered this freewheel. It doesn't seem to have internal splines.

Quick google leads me to believe I need an obsolete lockring tool. Is this true?

Honestly, I don't think this bike is going to be ridden—friend thinks they might ride it next spring, but they've had the bike for a least a decade, and I'm guessing it's been ridden maybe ten times. So I could just leave it, but the bearings feel a little crusty.
EDIT:
False alarm, it does have splines, and a Park FR-1 fits. Duh!

https://cimg7.ibsrv.net/gimg/bikefor...b548a05c24.jpg
MF-HG20 Shimano freewheel

Looks like a BB lockring tool would work.

It has internal splines for the freewheel tool. It's probably covered with crud.

I would bring it to the bike shop.
Most shops would remove/ loosen it on the spot.

They MIGHT charge you a few dollars.

My shop does not charge...at least me :)

Well, this is a bit embarassing:
To answer my own question: as Retoocs said, it does have splines, I just didn't see them for the crud.

Park FR-1 removed it once I leaned on it with a long wrench.

Thanks for all the responses. Sorry for the false alarm!

As the bard said: "All's well that ends well." :) Glad you were able to help your friend.