I was going to mention to install GPU-Z or SPECCY but both aren't supported in Linux. But did find one similar to both that can be used in Mint called HardInfo.
Here are two websites that shows how to install Hardinfo in Mint and other Linux Distro:
1) [Solved] Linux alternative to Speccy? - Linux Mint Forums
2) How to check graphics card on Linux - Xmodulo
At worse, you can remove the GPU card and locate the Serial Number and Part number and if you know the Manufacturer of the GPU card via HardInfo you can open a Support ticket and they should be able to tell you exactly what GPU card you have according to the serial number and/or part number. This is usually located on a sticker label on the actual GPU card.