Serializing the current state of "Module Random" in OCaml's StdLib

I must have read the OCaml manual page on the standard library modules Random and Random.State half a dozen times (probably even more often) but I can't figure out how to serialize the current internal state of the PRNG.

Here's what I learned so far:

• The modules Random and Random.State both operate on a state that is abstract / opaque from the outside.

• Both modules offer two / three initializers, but functions exporting the current state ... I can't see them :(

What can I do ? Help please !