Identifying Specs of Used MacBooks

Solution 1:

The serial number should be printed on the back and can be used on https://everymac.com/ultimate-mac-lookup/ to get the spec details. Unfortunately this will not show built-to-order details, so your best bet is to charge and boot (at least into Recovery) those which look interesting.

Solution 2:

If you want to see build to order specs you can boot the mac into recovery mode and start a terminal.

Then you can use the /Volumes/Macintosh\ HD/usr/sbin/system_profiler SPHardwareDataType SPHardwareDataType command to get a full overview of the hardware.

To boot into the recovery mode, use command + r on startup.

This does require however that the previous users did not set a firmware password. If you bring a wifi hotspot or an ehternet cable (with the appropriate adapter) you also could boot newer Macs to Internet Recovery, so there are lots of options to get detailed information even if you might be foiled by an account password that’s missing.

Solution 3:

The other answers already cover how to extract the specs so I want to touch on this piece:

I am to visit a storage unit full of relatively new ( 2015 - 2020 ) used MacBooks to pick one for myself.

What? is this normal?

Do you plan to buy a laptop without making sure it boots up?

Shouldn't a charger be supplied with the laptop you choose?

Shouldn't the seller have specs posted? How do you know the price before you pick it up?

Why aren't these machines already factory reset and bootable? If you can't get to the system info screen then how can you trust what you see?

I'm hoping they have their specs posted somewhere so all you need to worry about is verifying specs right before handing over your money.

Something seems quite fishy...