PrimeAsia's wet blue hides are physically traceable back to the specific slaughterhouse of origin through a process of physically stamping all hides. PrimeAsia is audited on the ability to trace their hides back to the slaughterhouse during their Leather Working Group Audits. Both of PrimeAsia's tanneries have 98% and higher traceable hides. The traceability rating of both tanneries is listed on their LWG audit certificates under their medal ratings.
For more information see the Leather Working Group's website for how the organization audits traceability.