If it's been repainted you probably won't find out what the manufacturer is, as the serial number is next to useless, and it's not all that important. If the bike has welds and equipment typical of a better bike (rather than a Huffy, etc.) there is not a great difference between brands of the same level. How to determine the year value etc of your bicycle
HOWEVER - Mongoose serial numbers started with a letter or letters, not numbers only.
I’m happy to help further over the phone at https://www.6ya.com/expert/donald_f2ed37026a3ac881
Answers & Comments
If it's been repainted you probably won't find out what the manufacturer is, as the serial number is next to useless, and it's not all that important. If the bike has welds and equipment typical of a better bike (rather than a Huffy, etc.) there is not a great difference between brands of the same level. How to determine the year value etc of your bicycle
HOWEVER - Mongoose serial numbers started with a letter or letters, not numbers only.
I’m happy to help further over the phone at https://www.6ya.com/expert/donald_f2ed37026a3ac881