Hello, Tom -
I hope I am correct in thinking you are asking about a user manual for the Regent Corp. outdoor floodlight (not a rainlight) MS550. If so . . .
That model of outdoor floodlight was manufactured by Cooper Lighting, a division of Cooper Industries (headquarters: Peachtree City, Georgia), which is a division of Eaton.
I have not yet found the user manual online in any format.
Therefore, I suggest you contact Cooper Industries Customer Service directly and ask if the user manual for the MS550 model lighting (no longer manufactured and sold, apparently) is available. The company Archives may hold a copy which can be scanned as a PDF document for you. There may be a cost for such a manual.
This is the link to the Cooper Industries (Eaton) web page with a form you can fill out to send an email: