That is a watts LF009M2 Installed Vertically (Flow Down). As You know, This is a mistake.
USC Approved Backflow Preventers and Installation Guide.
Please click the above link to verify your backflow preventer has gone through the strict requirements of the laboratory testing at the University of Southern California.
The above link also provides information on installation approvals for horizontal or vertical installation.
If the backflow preventer is approved for vertical installation please note if it’s approved for Flow up and Flow down. Most backflow preventers are not approved for vertical installation, but some are. For those assemblies that can be installed vertical, most can only be installed flow up.