"apt-mark showmanual" will show you all packages that you have manually installed
"apt-mark showauto" will show you all packages that are automatically installed
"apt-mark showinstall" will show you all the packages that are installed
How is this useful? It tells you what packages are installed in your system.
So you can go "apt-mark showinstall | grep somelibrary" to see if you have a particular library installed that's a dependency.
VINTAGE COMMODORE VIC 20 COMPUTER **BR0KEN
$79.95
Commodore 64 Personal Computer Keyboard W/Box, Power Cord, Tested/Works
$150.00
Commodore 1901 Monochrome Monitor, TTL, 9 Pin, 1988, RARE
$145.00
Professionally Restored NTSC Commodore 64 | Cleaned, Recapped, and Guaranteed
$289.00
Vintage Commodore VIC-20 1981 POWERS ON w/ power brick
$50.00
Commodore 64 NIB Never Used. Deck Only, No Cables. Box In Decent Shape
$200.00
Commodore Vintage 1983 Monitor Model 1702 Tested Works See Photos
$340.00
Commodore International VIC-1525 Graphic Printer
$105.99
Commodore MPS-803 Dot Matrix Printer in Original Box Powers On Printhead Moves
$40.00
Commodore 1541 - 5.25" Floppy Disk Drive for Commodore 64 System in Original Box
$65.00