Sway Bar Bushing Question of Historical Significance

[Sunroof]

Okay.....this one is interesting........

My 1973.5 T takes 15mm ID sway bar bushings and I found one at a shop here that had the red (more like mud color) circular insert that was a hard but pliable compound that was different then the surrounding black rubber. The packaging label showed signs that it was on the shelf for a couple of decades.

The manufacturer was German; however, when I went to the dealer to purchase the other three to finish the job, I noticed that they made a change and no longer used that "bullseye" insert feature, but all black rubber. Same manufacturer, and Porsche part number, just different compound. I would imagine they were popular 30 years or so ago.

I am not trying to get into minutia here fellas, but I am trying to slowly restore this car back to original and some would have a field day with this issue.

If anyone knows what I am talking about I sure would like to know why the changes in bushings and what that insert is made of. Simply, I am curious to find something out.

Regards,
Bob
73.5 T