for thos interested in the topic the following link may help you in understanding:

http://www.jstor.org/sici?sici=0007-6805(197222)46%3A2%3C182%3APTPOAS%3E2.0.CO%3B2-M&cookieSet=1

It is an article cited best as:

• Petrobrás: The Politicizing of a State Company, 1953-1964

• Peter Seaborn Smith
• The Business History Review, Vol. 46, No. 2 (Summer, 1972), pp. 182-201
• Published by: The President and Fellows of Harvard College

look also at the American influence, partly looked into at:

http://www.jstor.org/sici?sici=0003-1615(199410)51%3A2%3C193%3ACALANU%3E2.0.CO%3B2-V

to be cited as:

It is necessary to look at: Law N° 2004 of October 3, 1953

on the company and some of its history:

http://secfilings.nasdaq.com/edgar_conv_html%2f2007%2f06%2f26%2f0000950123-07-009192.html#FIS_COMPANY_INFORMATION

Here by the way is a picture:

Here is what Petrobras has to say:

Bearer Bonds were instituted by art. 15 of Law Number 2.004/53, dated October 03 1953, and they resulted from the yearly compulsory contribution car owners had to pay from 1954 to 1957.

These bonds could have been converted into preferred shares issued by PETROBRAS, as long as the bond holders complied with the requirements of the Joint Stock Company Law and of art. 18 of Law Number 2.004/53.

In order to facilitate the conversion, from 1957 to 1963 Petrobras undertook public share subscriptions to increase its corporation capital. The service rendered to those interested in redeeming the bonds or in converting them into PETROBRAS shares was done throughout the Country through an extensive network of bank branches, an effort previously divulged by the Press.

It so happens, however, that the Bond values, printed in "cruzeiros antigos" ("old Cruzeiros") (currency in effect at the time) could not be corrected since these titles had been issued between 1956 and 1959, and monetary correction was only instituted in the Country in 1964, therefore, the bonds had no representativeness in the current exchange.
Furthermore, more than 20 (twenty) years later, bond holders who had not manifested themselves in the due period of time could no longer request to receive the redemption value or request conversion since this right was not exercised in the period provided for by law or in the conditions mentioned on the back of the bonds themselves, which caused the bonds to expire.

We must emphasize, finally, that the Republic Presidency's Citizen Right Defense Commission (Comissão de Defesa dos Direitos do Cidadão, CODICI), in a decision made on 07.20.88, in suit Number 3.337-5/87, concluded no rights had been violated by bond prescription or under art. 18 of Law Number 2.004/53.

Last Update: April 2008

source:http://www2.petrobras.com.br/ri/ing/InformacoesAcionistas/AcionistasMinoritarios.asp

in another forum someone posted the response he received when inquiring with the company:

Dear Sir,

I regret to inform you that those bonds are no longer valid. Please, take a
look at the back of one of those bonds, and on the right hand side you will
read in Clause 1(even though in Portuguese) what the expiration date was.
Depending on the Serie, it was Dec 31st, 1977 or, at most, 1980.
Moreover, due to previous claims, there is a decision by the Civil Rights
Defense Commission, from the Office of the President of the Republic,
stating that the owner could either have claimed the amount or have had
the bonds converted into stocks from January 1st, 1958 until Dec 31th,
1977.

Best Regards,

Alexandre Velloso
Renda Variável / Equity Investor
Relações com Investidores / Investor Relations Department
Tel: (55-21) 2534-3879
Fax: (55-21) 2534-6055
E-mail: avelloso.hope@petrobras.com.br

see: http://www.secinfo.com/d125Cx.221.htm

Announcement

(Rio de Janeiro, September 30 , 2003). – PETRÓLEO BRASILEIRO S/A - PETROBRAS, [Bovespa: PETR3/PETR4, NYSE: PBR/PBRA, Latibex: XPBR/XPBRA], a brazilian international energy company, in order to dispel doubts regarding possible losses arising from frauds in connection with securities issued by the Company during the 50s, wishes to state that:

• The securities mentioned above are Bearer Bonds which were introduced by art. 15 of Law no. 2.004/53, of October 3, 1953, and were based on the annual compulsory contribution to which vehicle owners were subject from 1954 to 1957;

• These securities paid half yearly interest and could have been redeemed or converted into preferred shares issued by PETROBRAS, at the end of 20 years - during the 1970s - if the requirements of the Corporation Law and art. 18 of Law no. 2.004/53 were satisfied by the bond holders;

• After 20 (twenty) years, bondholders who did not demand redemption or conversion in due time could no longer do so, as they had not exercised this right within the time limit laid down by law and in accordance with the conditions stated on the back of the bonds themselves;

• Given “that such bonds are not SHARES, but may be converted into shares, provided that redemption or conversion was demanded, at the appropriate time ”, the Presidential Commission for the Defense of Citizens’ Rights (CODICI) in a decision dated August 19, 1988, handed down in case number 3.337-5/87, took the view that no rights had been violated, as they were statute barred and in view of the provisions of art. 18 of Law number 2.004/53, which laid down the conditions to be satisfied by each person requesting redemption or conversion.

It should be emphasized that the Company has suffered no loss from the fraudulent attempt to redeem these securities.

Contacts: