Yes it looks good but with the quality and extent of the engraving it's very doubtful that it was an issued weapon, it's more of a commemorative knife. However, that does not mean that it was a cheap knock off of a K-bar.
1. To the best of my knowledge the USMC never issued a commemorative knife.
2. 25$ is inexpensive. Buy one and give us a test report.
3. Most marines are very likely carrying the current standard issue made by Ontario ,oks-3s