I started to flatten the back, then stopped, as I realised they had sent me the wrong chisel.
I contacted the same retailer, and purchased the chisel I was after, without having to pay postage, but decided against returning this one for a refund thinking I'd be able to sell it to a UK woodworker around Christmas time! ( I had had enough of the long distance merry-go-round in a foreign language and of courier companies)!
£75 including postage to mainland UK
I found that buying from Japan can be problematic, the difficulties are often with the couriers who sometimes add charges to cover the increased admin they face with import regulations. I am hoping to get my money back.
Hopefully sending within the UK will make this a straight forward sale.