This is taken from a seminar at the National Polytechnic Institute Higher School of Business and Administration in 2007. The topic was internal control of registered trademarks.
Here is a link to the resource that lists the transfers of trademarks to Mexico- only helpful if you read Spanish though.
http://itzamna.bnct.ipn.mx/dspace/bitstream/123456789/275/1/Binder14.pdf
I have included what I thought was pertinent to this discussion - the translations are my interpretation.
En 1962 con tan solo 10 empleados nació Herramientas Nacionales, S.A. de C.V. en un taller en el barrio de Tepito, en la Ciudad de México, donde se produjeron herramientas esenciales para el ramo de la construcción como martillos fundidos, cinceles, cucharas de albañil y plomadas para la marca Herna.
In 1962 with only 10 employees, National Tools was born in
a shop in the barrio of Tepito, in the the city of Mexico City, where they produced essential tolos for the contruction field such as forged hammers, chisels, trowels, and plumb bobs with the brand Herna
En 1967 una empresa Estadounidense se asoció con Herramientas Nacionales y se ampliaron las instalaciones a 3,300 m2, dando lugar a la fabricación de nuevos productos como martillos forjados, tijeras, bieldos, rastrillos y zapapicos.
In 1967 an American Company associated with National Tools helped develop the Factory to 3,300 square meters, allowing space for the fabrication of new products suchas forged hammers, scissors, rakes, files, and picks.
En 1968 los productos fabricados por Herramientas Nacionales se comercializaron con las marcas Papagayo y True Temper.
In 1968 the products made by National Tools were marketed under the name of Papagayo and True Temper.
En 1973 Herramientas Nacionales compra las acciones de la compañía estadounidense True Temper. Ese año, se compra el primer terreno en Jilotepec, Estado de México, donde se construye la primera planta y se adquiere la maquinaria para la fabricación de mangos de madera.
In 1973, National Tools bought the rights to the American company True Temper. This year, the first plant in Jilotepec, State of Mexico was the first plant to acquire the machinery for the making of wooden handles.
En 1975 surge formalmente la marca TRUPER sustituyendo las marcas Papagayo y True Temper.
In 1975 the branding of TRUPER was oficially substituted for the names of Papagayo and True Temper.
The entire Truper/True Temper buy up story is there if you want it. I stopped reading after "China" was mentioned in order to achieve "clean factory" certification.
It is mentioned that an American company assisted National Tools in their site preparation. I wonder if it was the American Fork & Hoe Co. that assisted in production to get the name going and apply some capital before transferring to True Temper production in Mexico?
There must have been a very small window for this hoe to have been made in the US before the name rights being transferred to the Mexican plants.
Steve I followed that link and I think you got a winner! The humps near the eye are identical. Didn't see hoe or "azada" being listed in the seminar program. Used to be a pretty good-sized hoe, shame. That was fun.
https://imgur.com/a/WcjaD
IMG_20171027_161941
Do it. Take the pic 
