How rare are unbranded ThinkPads?

[GimmickTadpade]

I recently rescued and fixed up a ThinkPad T60 and noticed that it doesn't have any Lenovo branding on the screen bezel or the bottom sticker. How rare are these units? Are there any specific reasons or historical contexts that explain why some T60 models might lack the Lenovo branding? Additionally, could the absence of branding affect the value or collectibility of this laptop compared to other T60 models with standard branding?