It's a Joseph Allen & Sons, Rob - Lose The Beard got there first!
No 'England' on the stamp, so no later than 1891 when the McKinley Tariff Act became law (although it only affected items made after the Act was passed - ie post 1891). Apart from that, the company moved to the Eccleshall Works in 1891.
The earliest date for the razor is hard to give, as I can find no hard facts regarding when the Oak Works in New Edward Street were acquired. It is known that he was in the Oak Works 'by the late 1880s' but not precisely when.
He is recorded as a 'razor back forger' residing in Rockingham Street in 1871, as a 'razor manufacturer employing ten men' residing in Solly Street in 1881 and as a 'cutlery manufacturer' residing in Crooksmoor Road in 1891. He died in 1893.
Regards,
Neil