French term (edited): barrette fond

i've no diea if there is a more formal technical term for this, but I would understand it as being a relatively plain area to be left, perhaps for later engraving, etching, etc. So 'fond' in the sense of a 'background'.

Presumably 'barrette' refers to the fact that this is often a strip suitable for, say, one line of engraving — perhaps the actual articles being moulded here may give you some idea?