Plasticca 450mm F3.5 dimensions

[mhayashi]

I’ve recently acquired the Plasticca 450mm F3.5 version.
i was surprised the lens size isn’t large enough considering it’s focal length and f-number.
Do any of you guys have either 450mm F3.5 or F4 verisons and check the dimensions?

I thought the size should rather be 450mm/3.5=128.5mm but the actual lens diameter is about 96mm and there is a black inner rim as shown in the second picture, whose hole diameter is 87.7mm. these numbers show the f-numbers are 4.6 and 5.1 each.

How about is yours?

I saw a related thread of Steven’s here.
https://www.largeformatphotography.i...ight=Plasticca

Thanks for your help.