If you're not talking out your ass then the 4 will only have 10 years of service. Steam stopped adding to the years of service badge on empty accounts after 2013. If it's empty and doesn't have the 10 years badge, then you or someone else removed it via Steam Support.
Will look like this.
If it has > 10 years and is empty, then you or the one you bought it from is lying.
Accounts without HL1 Plat that weren't logged into periodically were deleted ~2007. In order for a low id without HL1 Plat (whether it be 1.6, hl1, empty) not to be deleted, the original owner had to log into it every now and then pre 2007. Which almost never happens, because if I'm not going to buy your games after having my account for 4 years, why would I log into it every now and then?
Seeing as you don't know any of this makes me question why you said I know nothing, but let's not derail the thread anymore.