How do I find out who has my account from some penny stock I bought in
1988.  The receipt has a heading of H.T. Fletcher Securities,Inc: 2424
N. Federal Hwy.
Suite 220  Boca Raton, Fl 33431  -800-327-8130.  I cannot reach them. 
I would like to sell these.  It also states that the account is
carried by Securities Settlement Corp:  One Whitehall Street  New
York, NY 10004  1-212-709-8000.  I can't reach them either.  Can you
tell me if these companies have merged or gone out of business?  How
do I contact them?

Well it looks like Citigroup Inc is now the owner of thr previous
company. I hope this helps.

financial institutions on the West Coast. Likewise, Securities
Settlement Corp. in New York City, a subsidiary of Travelers Insurance
Co

http://www.mitchellmoss.com/articles/backoffice.html

1965
Becomes The Travelers Corporation, holder of Travelers Insurance Co.
stock and its former subsidiary Travelers Indemnity Co.

1995
Travelers Insurance completes the sale of its group life and related
businesses to Metropolitan Life Insurance Company; the two companies
form a new health-care company, The MetraHealth Companies, Inc.

http://www.citigroup.com/citigroup/corporate/history/travelers.htm

Metlife has since bought Travelers Insurance.

I couldn't find anything to reference how much your stock is currently
worth, or if it's even still valid.  Metlife is currently selling for
$40 per share.