It is common for collectors to confuse the European 5502 with its American and Japanese counterparts. While they are all "Version 3.0" software, they are region-locked:

Features the PU-18 main board, part of the "Hardware Rev. C" cycle.

The SCPH-5502 BIOS corresponds to of the PlayStation OS. While earlier European BIOS versions (like v2.0 found in the SCPH-3002) served the same purpose, v3.0 is often preferred in the emulation community for a specific reason: stability.