Actually about 5.5 links to the inch, 65 per foot ladder chain for transmission/roll motor. Less commonly used on player pianos than 4/inch but still encountered on some Baldwins and a few others. Sold by the foot, orders of more than 1 foot will be shipped as one continuous length. 

The chain is steel that has been copper plated. I've restored player pianos for 30+ years.  If you have questions about this product before or after your purchase let me know, I'm glad to help.  I include my contact information with each package and you can also reach me through eBay.