Here is what I believe to be a production engineering prototype of the Titanium 75. It is distinguished by the barrel end tassie which, like the cap tassie, is flat. This feature is like my first prototype of this pen, shown as prototype #15, #25, #38, and #39.
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The other interesting thing to note is that the clip matches the flat tassie. It is the earliest clip for the 75, with a smaller arrowhead, shorter clip length, and longer arrow feathers.
The weight of this pen cap and barrel are 4.9 and 3.7 grams, respectively. At a total of 8.6 grams, this is the lightest Parker 75 FP I have ever seen.
As I wrote for prototype #15, I would speculate that this prototype was made sometime in 1970-71 when the T1 was first being introduced and sold. This was not something Parker did after they decided to kill the T-1. Why? Because by that time the clip and tassies for the 75 had already been changed.