Hello, I am looking at buying this certain older Wingmaster on Gunbroker. Looking at it closer the serial number is not under the Remington on the receiver like on all other wingmasters. Can anyone please help on if this is alarming or not?

I wouldn't be alarmed. Remington has gone through a few different cosmetic variations of wingmasters.

If you can see the full serial number you can call Remington, give them the serial number, and they will tell you when the gun left the factory and can tell you if the serial number is in the right place. Maybe you have a collectors issue.