Where is coagulation factor v produced?
Factor V is indeed mainly produced in liver (Wikipedia), which releases it into blood plasma.
But platelets are also an important source of factor V and &quot;may account for &quot;~25% of the circulating factor V&quot; (ref 1)
Platelet factor V is synthesized in megakaryocytes (ref 1), which of course are the bone marrow cells responsible for the production of platelets.
The following reference gives a much more detailed explanation of factor V
Reference (available as free pdf)
Factor V Is Complexed with Multimerin in Resting Platelet Lysates and Colocalizes
with Multimerin in Platelet α-Granules *

Catherine P.M. Hayward
Emilia Furmaniak-Kazmierczak
Anne-Marie Cieutat
Michael E. Nesheim
John G. Kelton **
Graham Côté

Journal of Biological Chemistry (1995) Vol 270, pp19217-19224