It looks like a CK 2890 to me, but I still can't read the inside of the case back clearly. If it is a 2890, that would be a jumbo reference. The serial number would put the year of manufacture around 1952. Given that it's a waffle dial, I'm going to agree with Foo2rama and say that it's likely original. Dial looks to be in exceptional condition for its age and the crown looks correct. I can't really tell from the photos whether the case has been polished, but I would be surprised if it hasn't been. An unpolished case would be a plus. What's the asking price and do you know when it was last serviced?.