Please help me identify these marks

Can’t supply photo at present, so hope someone can help.
I have a hip flask which has MAQUARIE SHEFFIELD ENGLAND on the base, not sterling but has unusual marks.x3. First mark is a diamond shape with a circle inside of that and then a triangle inside the circle which has the letters B over PC. 2nd mark is a date letter
W inside a sheild shape, the " W" is very plain and is in capital. 3rd mark is a winged horse rearing its front legs with a sort of sea horse tail curled inwards!!
The flask is round rather than oval and has a round screw cap lid. On the front of the flask is the Harley Davidson Motorcycles logo, which is raised. I have exhausted every research avenue I can think of and have had no luck .
I really would like to know what the marks mean. I think it might be plate or perhaps pewter??
Cheers, Lin

The first mark you describe sounds like one used by the The Association of British Pewter Craftsmen. They were founded in 1970.

Hi snuffer,
Thanks heaps for that info. Im going to research that lead.
Cheers,
Lin