I hold a set of 10 Sterling Pound Gold Bonds "presumably" issued by
The Republic of Peru, on the 7th of June 1920. The Total amount issued
was 720,620 Sterling Pounds. The issue was of 72,062 bonds, of 10
Sterling pounds each. The front reads as follows:
?REPUBLIC OF PERU 5 PER CENT. GOLD BONDS OF 1920 FOR 720,620 STERLING
POUNDS. IN 72,062 BONDS OF 10 STERLING.? 
BEING THE AMOUNT OF AN ISSUE OF BONDS MADE IN CONFORMITY WITH LAW NO.
4131 OF THE SEVENTH DAY OF JUNE 1920 OF THE REPUBLIC OF PERU PASSED BY
THE LEGISLATIVE CONGRESS THEREOF, AND SECURED BY A GENERAL BOND DATED
THE 24TH MAY 1921 OF
WHICH A COPY IS PRINTED ON THE BACK HEREOF.
PRINCIPAL REPAYABLE IN STERLING (ENGLISH GOLD) ON THE 1ST JANUARY 1946
UNLESS PREVIOUSLY REDEEMED BY THE OPERATION OF THE SINKING FUND OR BY
THE EXERCISE OF TH OPTION RESERVED TO THE REPUBLIC BY THE GENERAL
BOND.
INTEREST PAYABLE IN LONDON AT THE ANGLO SOUTH AMERICAN BANK LIMITED,
AND IN PARIS, HALF-YEARLY ON THE 1ST JANUARY AND 1ST JULY IN EACH
YEAR.
What is the value of each 10 S. Pound bond, with all coupons attached,
today? Are they redeemable?

HI, this site refers to a 1921 Rep. of Peru bond as "defaulted",
cannot be redeemed, which robably applies for your 1920 series.
  
http://www.museumofmoney.org/exhibitions/securities/hs09.html

But there may be a collectors' market for your certificates.

http://www.scottwinslow.com/

This site offers the 1921 bond for 50 Euro (ca. US$ 65), which, of
course, doesn't  say anything about the value of the 1920 issue.

Good luck