I know that browsers show no difference to the user between OV and DV certificates, but what is a sure way to find out if a certificate IS or ISNT an OV certificate?
Also, are there any technical differences in the cert?
Another answer partly answers your question: How does an end user differentiate between OV and DV certificates?
DV certificate contains no identifying information in the organization name field. Typically, this value just re-states the domain name or simply says "Persona Not Validated".
The organization name field is not part of a domain validated certificate.
Additionally, the policy identifier is different for DV and OV:
- Domain Validated: 220.127.116.11.2.1
- Organization Validated: 18.104.22.168.2.2
You can find this field in Extensions > Certificate Policies.