Watch List notes:

BANKNOTES, MISCELLANEOUS, Mexico, Real del Monte Mining Company, Silver Mine Share Certificate for a ½-Share, 1829, all instalments signed, dated and stamped, to the value of £30, paper watermarked Smith & Allnutt, 1828. Trifling wear at corners of folds, a crisp clean example.
The Real del Monte Mining Company was a silver mining operation in Mexico under Cornish management and employing miners from Cornwall. By the time it collapsed in 1849, it had lost over £500,000.

Estimate: £25-45