Have a neckless clasp has napier pat. 4,774. 743

... and what?

Are you trying to sell this item or what?

https://www.etsy.com/listing/23527477/napier-heavy-link-vintage-necklace-pat

Gold Napier Bracelet stamped PAT 4 774 743 | eBay (http://www.ebay.com/sch/sis.html?_nkw=Gold+Napier+Bracelet+stamped+PAT+4+7 74+743)

Jewelry clasp - The Napier Co. (http://www.freepatentsonline.com/4774743.html)
That is a patent number and has no bearing on gold content

Real gold is marked with the karat weight, 10, 14, or 18 K