need help with hallmark

I need help with this hallmark on the egg warmer.
I think its silver plated, Sheffield, Harrison Brother and Howson. but I want to know the date when it is manufactured.
Thanks for the help.
silber 003.jpg

You are correct in your identification of Harrison Brothers & Howson as the manufacturer. Unfortunately it is not possible to give a date as there is no reliable method of dating electroplate.