I beleive its a Felipe V 1738N 1/2 Real. Obverse : Crowned PHILIPPVS monogram, L at left and N at right, ( date )below; "PHILIPPVS·D·G·". Reverse : Quartely of Lions and Castles inside an 8 lobes border; L at left and N at right; "·HISPAN·ET·INDIARVM·REX·". Just do some googling and you can try find its value, I believe it's reasonably rare.