Today’s pen seems to be the actual Platinum relative to that Spanish pen. It is the Platinum Honest 60 pen from 1956.
The Honest 60's inscription on the barrel. Very different to that on the Spanish Presidente.
The top jewel, however, is the same on both pens.
Apparently, this Japanese company released the Honest model in 1955 with a bulb filler (according to Ron Dutcher, of Kamakura Pens). In 1956, the pen was marketed as the Honest 60 with a cartridge/converter system: “Good bye, ink bottle” was the pen’s motto at the time. This pen was, in fact, the first Platinum’s cartridge/converter model. In 1953, the ten year durable nib had been introduced and, therefore, the10 years imprint. The number 60 made reference to the company’s goal to become one of the top ten pen companies by year 1960.
This ad was taken from the Platinum's website. It speaks of the Honest 60, but the pen shown is the later model Honest 66. The date —Christmas '60— is correct for the later 66 model.
The Platinum Honest 66 (P66-100) model. A mayor difference with the older 60 model is the smooth barrel on the 66 versus the stepped one on the 60.
In 1959, Platinum realized that goal could not be accomplished and put it off to 1966. And a refurbished Honest pen –the Honest 66 model, code number P66-100— was released.
The Honest model here shown is the cartridge/converter model from 1956. And this filing system is the basic difference with the aerometric Spanish relative. The rest are mere cosmetic differences. Even the steel nib is engraved in the same way: “PLATINUM / (Company logo) / 10 YEARS / HONEST / (JIS logo) 11”.
Then, how did the aerometric Presidente become Spanish? How did the bulb filler or the cartridge/converter system become aerometric? Was the aerometric some sort of production test for those pens finally sold in Japan? I have no answers for these questions, but at least here we have the obvious relative to that not-so-honest Spanish pen registered by some Doroteo Pérez y Pérez in 1959. And the quest for information continues.