I’ve noticed this as well. I just received an order of t100s irons that were bought from someone else and my 8 is rounded and not square.

Here is a picture of my 8 iron. Ordered through a Titleist Fitting Day. My T100Sii are 2 degrees flat which may help explain why the difference. KBS Shafts and serial numbers on each iron similar to the bottom photo of the T100ii.


IMG_8927.jpg

I also went to my local Golf Galaxy and saw a set on the rack. Ironically the 8 iron and PW are the two clubs that are most noticeably different. The ones at Golf Galaxy had the round 8 iron and more square PW.

It looks like the top set doesn't have the underscore on the 6/9 irons. There is also the possibility of 2019 and 2021 T100 versions may have different fonts - the differences in appearance are subtle.
If buying in the secondary market the key thing to do is get proof of the chain of ownership. Even if buying from a good buddy, that isn't a guarantee w/o a proof of manufacture shipping..
For reference, my T300 2021 have the square 8 and the 6/9 underline.

I was intrigued to check this when I got the T100S, mine has a rounded 8 with 6/9 dash - like the bottom photo.

In comparing the pictures above, I’m noticing the top is a pic of T100S, while the bottom is T100 - notice the PW loft difference. Don’t think it explains way the two fonts, because my T100S looks like the T100 photo. Maybe manufacturing plant difference?