The GS748T versions can be identified by the serial number prefix.

There is no hardware upgrade.

GS748Tv1 serial number starts with GS27, 141, 1DT, 1LC, 1MC or 1PK.

GS748Tv2 serial number starts with 1MB.

GS748Tv3 serial number starts with 1RB.

GS748Tv4 serial number starts with 2H3.

GS748Tv5 serial number starts with 3H3, 3H4.

Remark:
Firmware for v1 cannot be used for v2/v3, v4 or v5 and vise versa.

Firmware for v2 and v3 are compatible.

Firmware for v4 are NOT compatible with other versions.