Help value ing late 1700s 1/4 guinea gold coin

Hi hopefully someone more knowledgeable then myself may be able to help 

I have 1781 or possible 1812 gold shield quarter guinea 

Weights 1.75g ..

24ct gold as far as I know 

Unfortunately I have no idea of value 

Be a shame fo sell for scrap 

N#13141

24ct in metric is 100%. Period British gold coinage was not minted at that fineness.

Large shield design is not used after 1786

¼ guinea was minted only in 1762-64 and used smaller portrait.

Your coin is over 10% below weight of ¼ guinea.