Yes its 180mm between centres which is awkward as most standard pear shape anodes are 200mm. You can get around this by elongating the holes with a file or alternatively ask Finland to send you an original.
Further to my above post just to clarify: The anode fastening studs which protrude through the the Hull have 180mm between centres. Most suitable anodes in the UK are designed with the fitting bracket slot on to studs with 200mm centres. Ten minutes with a file will allow you to extend the slots in the anode bracket so they will fit over the studs on your 331, its a job I do every time the anode needs changing.