Help identifying gold bond coupons

News: Welcome to the Canadian Paper Money Forum.

Hi, I came across this interesting sheet of coupons that appears to be part of some sort of gold bond. I haven't found much information on them, and what I have found is rather confusing.
I believe they were initially part of a larger sheet. They appear to be gold bond coupons issued by the city of Frankfort-On-Main, which my searching is turning up Germany, but they are redeemable in Boston, New York, or Chicago at the offices of the company E.H. Rollins & Sons.
Can anyone find the story with these? Why would a German city offer bonds that are payable in a different country?
Also, any idea on the value of something like this? It's in rough shape, and based on examples I could find online, this one is probably only worth a couple bucks, but other opinions are welcomed.

You have coupons from a $1000 German 25-year Sinking Fund 6½% Gold Bond issued in 1928 and due May 1st, 1953.  I have seen complete bonds with intact coupons in online auctions realizing between USD $100 - $300 depending on condition.

Gleaned from some Internet research:

In 1928, the city of Frankfurt on Main issued an American redemption fund loan through the New York bank E. H. Rollins & Sons with a volume of $ 6,250,000. The bond was to be redeemed from 1929 to 1953 by draw at par (redemption fund loan). The proceeds of the bond were intended for the expansion of the city's electricity, gas and water works, tram network, ports and docks, slaughterhouses and cattle yards. Up to and including 1932, the bond was settled in accordance with the contractual agreements.

According to the law enacted in 1933 on payment liabilities to foreign countries, the payments (interest and repayment) of the bond by the City of Frankfurt on Main could no longer be addressed directly to the American creditors in dollars. They were to be paid from Frankfurt on Main in Reichsmark to the conversion fund for German foreign debts in Berlin, which assumed the obligations towards the foreign creditors. The conversion fund only partially fulfilled the obligations of the bond contract of the city of Frankfurt am Main until 1945, since after the entry of the United States into the war (1941), the conversion fund could no longer pay any amounts to the American creditors.

Due to the London Debt Agreement on German foreign debt of 27 February 1953, which became legally binding between the United States of America and the Federal Republic of Germany on 16 September 1953, the City of Frankfurt on Main was able to resume payments from this foreign bond. The settlement of the remaining debt from the 61/2% Twenty-Five-Year Sinking Fund Gold Bonds, Municipal External Loan of 1928 was made in accordance with the regulatory offer of the City of Frankfurt on Main of 1954 by exchanging the bonds into 4_7/8% City of Frankfort-on-Main Municipal External Loan of 1928 - Extension and Funding Issue of 1952 – Sinking Fund Bonds, Due May 1, 1973.

Thanks! That confirms the information I was able to find. I just thought it rather odd that a German city would have bonds payable in a different country, and not even one geographically close.