David Gray was a prolific Dumfries maker, recorded as working between 1814 and 1841. He is also known to have worked with Joseph Pearson prior to this. The three marks of the Unicorn, the "G" and the fouled anchor are fairly standard for his work although he did also use other marks, including a "K", "S" and a Stag's head.  These tongs are fairly ordinary fiddle pattern with concave and squared arms. I would estimate them to be dated around 1820 to 1830.