8976 MLN

The numbers indicate the distance from this bridge to Paddington, the railway terminus, in this case 89 miles and 76 chains (there are 80 chains in a mile, 10 chains in a furlong, 8 furlongs in a mile, but the early railway engineers did not bother with measurements in furlongs). 'MLN' provides further information indicating the bridge is on the Great Western main line.
Canon EOS 30D + Canon EF100-300mm f/4.5-5.6 USM lens.