Carapace appears cut.
The upper and lower "shells" are held together in a manner that short of smashing ,usually stay together. With age and exposure ,the plates separate on the top/ back.
The o.p is a half of a belly plate,different in that they ,depending on specie ,are softer when live.
The cut area separating the upper and lower is where we used to separate shells on snappers.
Holes i've not seen like those.
Only my opinion but the piece in original post looks worked to me.
Turtle was a popular clan, part of some mythologies,..as well as meal.
Thank you so much for the feedback. The holes really looked hand drilled. I am not sure that an animal would do such a thing so symmetrical. I assumed it was man made, just unsure how old it is.
I cant say either way but you need to read everybodys responses and accept each one. Nothing against CHAIR but I noticed just as soon as somebody said yes or maybe the OP jumped rite in and excepted it as fact. I can enlarge the pics enough to see the holes dont look drilled to me they look to jagged if they were drilled they would be smooth. I need to know the state and we need to see front and back photos.
...they also look well chewed by a rodent...
From what I see there is a lot of rodent chew marks all over the shell and a lot around the holes. If this was once a drilled item, then the rodents have done it in. You might want to talk with a fossil hunter in your area, they could tell you how long bone will last in the ground and that alone my give you your answer.