How to tell whether a .dmp is an EXP oder datapump?

When I get a .DMP from a customer - sometimes via another one or two colleagues, it's hard to tell for me - unless I'm trying to import it and see if I run inti an error - wheter a certain .DMP file is of type datapump or plain EXP. Is there a way, e..g. look at the first bytes or so?

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Christoph