Random carb question on 1968 18 hp evinrude

When I recently rebuilt the carb on my 1968 evinrude, I saw that it had a rubber tipped float needle, but did not have the spring, and didn't even have a groove for one on it. It looked just like the picture I've saw of the factory all metal needles but with a rubber tip. I was curious if anyone knew during what time period those needles were used. I know everyone emphasizes the importance of the spring with the rubber tips, but I assume that had to have been discovered at some point after a bunch of "new and improved" rubber tipped needles had problems with sticking, leading to the addition of the spring.

I know it really doesn't matter, but I'm just curious as to roughly when this carb was most likely rebuilt last, because by the screwdriver damage on the high speed nozzle it's clear that it has been worked on at some point, and I assume that particular part wasn't used for very long.

Re: Random carb question on 1968 18 hp evinrude

A quick scanning of the parts books shows the rubber tip needle with a clip appearing in 1976. The rubber tip without a clip was used briefly before the problem was discovered. Seems like I remember the problem beginning almost immediately when new motors wouldn't run. Now......no telling how long a replacement service part may have laid on the shelf before being installed in somebody's carburetor.