Here is a website that may help you find out who or what Plunkett was. I have only checked a 1900 directory, which shows nothing in Lime Street. If his business was a large one, it might just have been a registered office in a large building, while his real place of business was elsewhere.

http://www.historicaldirectories.org/hd/b1.asp

My guess is that Plunkett retailed or wholesaled these within the UK, rather than exported them. Razors are an unfruitful item for the archaeologist, for they are easy to carry and cheap to send, and anybody who travels takes his razor with him. Where they are found tells us relatively little.