The Largest and Smallest Hard Drives Ever Made
This is a 4 MB hard disk platter from 1961:
This is a 4,000 MB hard disk platter from 2004:
The 4,000 MB platter is the dot you see in the center of the first photo:
These are the largest and smallest commercial hard drives ever made, respectively.
The larger drive is from a Bryant Model 2 Series 4000 Disk File. The platter is 39" diameter and 1/4" thick. It is made of magnesium. This particular platter came from a drive that was originally installed at Collins Radio Company in Cedar Rapids, IA.
The smaller drive is a Toshiba MK4001MTD. The platter is 0.85" diameter.
A photo of the Bryant Model 2 Series 4000 Disc File, from the Computer History Museum: