From the 2017 Fairfield Brick Swap, 8/5/17
Weight: 42lb 9.5oz
Dimensions: 12 3/8 x 12 1/2 x 8 5/8in
Manufactured by National Fireproofing Corporation, also known as NATCO, in Haydenville between 1906 and 1958. NATCO existed in Haydenville Ohio from 1906, when they purchased Haydenville Mining & Manufacturing Company. They re-branded from National fireproofing corporation, to NATCO in the 1930’s. For more information on NATCO, see Haydenville Company History.
These tiles were used to carry wires and utilities underground. Many of these tiles would be connected in a row, then buried. They protected and separated the wires.