If the receiver is steel, then it can be filed and sanded smooth, if not exactly flat, and re-blued.
Or you can skip the file, if you are not experienced at draw filing, and spend rather more time at it with a couple sheets of wet or dry and a hard backing block. I have used a file with a couple layers of sandpaper wrapped around it. Use a straight back and forth action, aligned with the pattern in the surface already. Adjust the grit until you get a pretty good match with the factory finish marks. A solid, flat surface, with a sheet of sandp[aper taped down to it will work too, you move the part rather than the abrasive.
If you want it done fast, but with a far higher risk of screwing it up, use essentially what they did at the factory, a belt sander. I would say about a 120 grit with some wear on the belt, should get you pretty close to a match for the factory finish, but try a piece of metal first to see how it compares.
With a little emphasis on pressing down on the engraved corner, it will cut mainly there. Same if you move the part over a taped down sheet of paper as above, if you lean a little harder on the corner you want cleaned up, you can control the location it gets the majority of the cutting.
If the receiver is aluminum, a quick once over with abrasive paper to knock down the raised up burrs around the artwork, and then fill it and paint over the receiver with gunkote or whatever firearms paint you see fit.
I hope it came cheap!
The other solution, which is both cheap and easy, is to skip all that, use the living heck outta it, and enjoy yourself, and not worry too much about it. Anyone asks, make up some outrageous story about a wild weekend, too much Tequila, and a guy named Raymond that ended up owing you money.