Here you go
# sane-find-scanner will now attempt to detect your scanner. If the
# result is different from what you expected, first make sure your
# scanner is powered up and properly connected to your computer.
# No SCSI scanners found. If you expected something different, make sure that
# you have loaded a kernel SCSI driver for your SCSI adapter.
# Also you need support for SCSI Generic (sg) in your operating system.
# If using Linux, try "modprobe sg".
found USB scanner (vendor=0x04a9 [Canon], product=0x1721 [MP210 series]) at libusb:001:003
# Your USB scanner was (probably) detected. It may or may not be supported by
# SANE. Try scanimage -L and read the backend's manpage.
# Not checking for parallel port scanners.
# Most Scanners connected to the parallel port or other proprietary ports
# can't be detected by this program.
# scanimage -L
device `pixma:04A91721' is a CANON Canon PIXMA MP210 multi-function peripheral
# scanimage -V
scanimage (sane-backends) 1.0.20; backend version 1.0.20
Notice the first two options return a presumably different result. One being a Canon MP210 and the other being a Canon PIXMA MP210, respectively.
I'm wondering if the difference in the listing has anything to do with the difference between canon630u and pixma backends.
The output from sane-find-scanner is what, I believe, you were looking for