Unusual Kohler tub drain tool needed

I have a Kohler tub waste / overflow set that I'm replacing (installed around 1940), and I've run into a snag. The drain strainer doesn't use the standard X-shaped innards, and I need some sort of internal tool to unscrew the drain cover (strainer) from the tub drain.
Here's the shape I'm looking at:
http://www.cycleorings.com/drain.jpg
I could possibly loosen the thing by putting a drift or screwdriver against one of the two tabs and striking it, trying to knock it around counter-clockwise, but I'd rather not risk chipping the tub's porcelain. Everything else has put up a pretty good fight, probably due to its age.
Anyone seen such a tool that would fit that shape? Search engines aren't working for me here. Any ideas appreciated.
Thanks.
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Robert Barr wrote:

It looks like an 1-1/2" steel pipe just might fit. (IIRC, standard 1-1/2" steel pipe is pretty close to 1-7/8" OD) If it does fit, it would be fairly easy to make yourself a wrench by notching the end.
Or get one of these: http://www.ridgid.com/Tools/Internal-Wrench/EN/index.htm
Or this: http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber7353
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That's an excellent idea! I was considering hacking up a piece of plate steel, but that would be about 11 times more effort.
Thanks!

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Another way to make a tool would be to grind the edge(s) of a 2" X 1/4" piece of flat steel until it fit down into the hole. Use a pipe wrench or adjustable wrench to turn it.
Don Young
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