Can Anyone Help with this Bottle?

A man who is lucky enough  to have a very old bottle of Sherry has been in touch but neither he nor I know anything about it. We wondered if anyone could help. It  has a hand-written label “Xeres Rebello 1864”. We considered Rebello Valente, a vintage Port by Robertsons who had some connection with Sherry and were bought by Sandeman but ruled it out, and also Gonzalez Byass Rebollo bodega, but the spelling is wrong. Also we don't know if 1864 refers to the solera or to a vintage. Osborne's Oloroso Solera BC 200 was established in 1864, but I'm not sure if that helps. I came across a 1984 Heublein auction in San Francisco where a sample was opened and the Sherry was "drying out a bit, soft, lingering, round and featured a marvellous nutty bouquet, worthy of acquisition".