Hi Kerry, welcome to the forum.
It is probably not a private seal but John Alberty would be the vinter/company and 1815 the year of vintage, here in Australia we often get that style of cognac seal bottle and they date mostly from the 1850's to 60s yet have seals often with dates as early as the 1790s.
That is an exellent find you have there, they are really nice bottles to collect [] .