Based on what I see in his code, I’d guess he used a v1 Ethernet shield.
The version 2 shield uses a library named EthernetV2_0.h whereas
version 1 of the Enet shield library is Ethernet.h
(he uses the v1 library in his code, but it’s possible the file could have been renamed)
This isn’t positive proof, but all of the examples I’ve seen that dealt with v1 and v2
of the Ethernet shield, followed that naming convention.