Stamps on freeze plugs?

Daughter and I were stripping down our $200 4.0L on the engine stand today. It came out of a 97 ZJ with 270k on it but sounded much better than my old motor. Just working to clean it up and prepare to swap into the yellow xj. Back freeze plugs looked brand new and have an "MP" stamped on them. The side freeze plugs have "2005" stamped on them. Do those sound like original plugs? Or dare I hope that our motor is slightly newer-ish?

It could be some sort of replacement, rebuilt engine. Could also be that the plugs were replaced. Check the block and head for casting numbers, then google and/or take those numbers to your local mopar dealer for more info.