I have done some homework. I think your brake shoes were leather indeed.
MK Kashiyama set of brake shoes for cultus model number K9933 is leather, whereas K9933-01 is carbon.
MK Kashiyama leather brake shoes come in yellow box with MK logo and name printed in purple. The carbon-based variety comes in blue box with MK logo and name printed in yellow. Khan motors Korangi road and Nippon autos Sunset commercial area are currently stocking this. (Both are near to each other and hence Khan motors is also in Sunset commercial). Quality autos doesn't (as of today) have either brake pads or brake shoes of carbon type.
Also, leather ones look slightly brown, whereas carbon ones look exactly donkey gray. MK have a good online presence complete w/ online catalog (which can be accessed only through a Japanese IP, can somebody tell me a Japanese proxy host?) The website is all in flash so translate doesn't work. You can have a look here, the brake shoes on the left are carbon, the brake pads on the right are leather. Main problem is one can only distinguish when both materials are lying side-by-side.
UPDATE: I found out that SGP (Suzuki genuine, or factory-fitted) brake shoes for cultus are NBK D9007 FF. It is light grey and surely has material composition different than either the leather ones or carbon ones available in market. They have steel filing mixed, though, just like the others.
Apparently these 'FF' etc are friction ratings. Just like the API/SAE ratings on engine oil bottle suggests its performance, brake materials have ratings too. Never knew this before. For more info, plz follow:
Capabilities of Various Brake Pads (this document will try to download to computer then open. Harmless.)
Best Brake Pads & Best Brake Pads - Part 2
Right now I don't know which agency maintains these standards. There is a hint it is named FMSI. I'll find out and update.