Macs (imac and macbook pro) not showing year or type under About this mac

Were it only the iMac, I woulds suspect a Fusion drive that became "split"--the mechanical component not recognizing the SSD component.

However, you cannot get a Fusion drive in a MacBook Pro.

This is a long shot, but try reseting your SMC:

How to reset the SMC of your Mac - Apple Support

Neither of your computers have the T2 security chip, so sjip those instructions.

You may need to reset 2-3 times.

If that does not fix it, I suspect some unneeded utility like anti-virus or so-called "cleaning" apps. Both cause far more issues the the claim to fix. Do you have any of the useless-ware?

This is for the "split" issue:

How to fix a split Fusion Drive - Apple Support

Still not sure that will fix the missing date.

Were both computers bought new or used? If some of the data is stored on the drive, and the drives were wiped or replaced maybe the ID info was lost.

Also try using System Profiler in your Utilities folder. The opening screen shows a machine model code. SP won't fix anything but will at least add significantly to the body of evidence if the data is missing there as well.

From my 2017 iMac 5K:

The Model identifier code for a 2014 27" Retina should be iMac15,1.

Foe 2104 MBPR15 the codes are MacBookPro11,2 (2.2 GHz) and MacBookPro11,3 (2.5 and 2.8 GHz)

I have a medical appt in a few minutes so won't be able to check back for several hours.