This has an unusual data tag. As best as I can tell, this jeep is an M-38A1 “D”, at least based on m381.com page’s reference to the XM28 tag (see comparison tag here). This may have been one of the last converted M-38A1s into a “D” variant, given only approximately 50 were converted at the Detroit Arsenal.
https://www.facebook.com/marketplace/item/142356480990269
“Very old military Jeep serial number 51 call or text”