You may find these links helpful
http://www.figurines-sculpture.com/unknown-crown-pottery-mark-on-pie-vent-chinaman.html
http://www.figurines-sculpture.com/antique-bone-china-query-artone-bone-china.html
http://www.figurines-sculpture.com/artone-pie-vents.html
These discussions attribute items with similar marks to yours - ie just a crown backstamp with the words Made in England, to Artone Pottery- there is some information about the pottery and the type of wares they made that may help you decide if yours could be from that pottery.
The crown of course is probably the most common device used by Staffordshire potteries but it is unusual to see it without some other identifying initials or names. I would think from the style of mark it is relatively modern - 1960s on, even later than that. Of course it could be REALLY modern - like made yesterday in China. You would know from looking at the item in question.
