You can identify M’Boards make and model by the BIOS string. All you need do is write down the BIOS string & Brand EG Phoenix, AMI or whatever and then go to site that is the BIOS maker they should have a listing of what the BIOS string actually means.
From memory the last few digits denote the maker and model of the M’Board. However if you already know the Model just do a Goggle search of that model and you will find the maker very easily.
Some manufacturers do a good job of labeling their mobos with makers name and model no prominently displayed. Assume they are reasonably proud of their product. Some just print a model no, and some don’t provide anything intelligible.
Look for a model # in fairly large letters/numbers on face of mobo. Something like M7VIT or 8GI8K. You can google model # to find more info.
If it was a OEM board from Dell, Gateway, HP, etc., you will have to go by the OEM part number and try to find info on manufacturer’s site.
Any markings or other info you can provide would be helpful.
Or, as indicated in first answer, hook it back up and get BIOS motherboard identifier.