Some info on tin cans from the Parks Canada Prairie and Western Region Artifact
Coding Manual and from my research in the Canadian High Arctic.

A pull strip without key was in existence by 1844.  "The cases are made in two
pieces and are joined by a band of tin running around the canister, which may be
easily detached, and is the best way of opening them" .  A patent for this type
of opening was taken out in the U.S in 1872 (Judge 1914:13).

A Key-wind metal tear strip was introduced in 1866 (Sacharow 1970:10).  A
key-strip was adopted on meat cans in the U.S. in 1890 (Goldblith 1971: 44;
Judge 1914:41)

Key strip closures were patented at the Canadian Patent Office in 1892 (#40534),
1895 (50167) and 1897 (58142).

A cylindrical butter tin from the Greely expedition at Fort Conger (1881),
Ellesmere Island, Nunavut, is marked "Topocan Brand/Patented June 25/78" was
opened with a strip forming a re-closeable lid.

There are three styles of rectangular key-opened tins from the 1906 Robert Peary
site at Cape Sheridan, Ellesmere Island.  One has the remains of a paper label
"ARMOUR & COMPANY, CHICAGO, U.S.A...PACKED...1905.  These were most likely for
meat.

As for opening tins below the rim, as far back as the 1850 material from the
High Arctic, tins were opened both below the rim and on the lid.  Presumably the
decision of which method to use depended on the liquid state of the contents or
the availability of a tool to open them.  In the 1850's a chisel seems to have
been very popular.

Bibliography

Goldblith, Samual A
1971
A Condensed History of the Science and Technology of Thermal Processing.  Part
1.  Food Technology, Dec. pp 44-50.

Judge, Arthur I.
1914
A History of the Canning Industry by its most Prominent Men.  The Canning Trade,
Baltimore Md.

Sacharow, Stanley and Roger C. Griffen
1970
Food Packaging:  A Guide for the Supplier, Processor and Distributor.  Avi
Publishing Co. Inc., Westport, Conn.