Hi,
Short of metallurgic analysis and no photos, as a general guess. A blade that shows a darkening or staining, or rust, would be a high carbon tool steel of some kind. If it looks used and is still bright and shiny, it's most likely a stainless steel of some kind.
As a WAG, just for fun, sight unseen. Your Imperial could be either carbon steel or stainless. They made blades out of both types. The Japan marked knife, I'd guess is stainless.
Post some photos like babakanoosh45 said. You will better opinions.
dalee