Help identify Large Fossil 5 foot long Aquatic mammal

[eurocars]

I acquired this fossil
and was told it was removed from a local beach in the late 1920s its about 5ft long. about 2,000LB

any info on what it is, age or what its value might be would be amazing!

also have many more fossils and unusual rocks I will post soon.

thank you.

 

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