Tub is clogged. Can't remove Kohler overflow plate

[Seafood Licorice]

Hi - our tub is clogged and I was trying to see if I could remove the overflow plate to see if I can snake out any build up from there. It's a Kohler K7213-CP and has what appears to be a hex screw with a good deal of hard water calcification. I tried every wrench I had but nothing comes close to working on that screw. Any ideas of how I might get it out?

 

[Terry]

Looks like a Geberit drain from Europe. I wonder if it's a metric allen wrench you need for that.

 

[Sponsor]

 

[Reach4]

Can you pick the deposits (looks like to me) out with a metal dental pick or small flat jeweler's screwdriver?

 

[Seafood Licorice]

Looks like a Geberit drain from Europe. I wonder if it's a metric allen wrench you need for that.

Thanks! I only had a US allen wrench set. I will try metric.

 

[Seafood Licorice]

Can you pick the deposits (looks like to me) out with a metal dental pick or small flat jeweler's screwdriver?

I will try that - I have a small screwdriver that might work. Very difficult to see what's going on in there based on the angle.