The "e" means "enhanced".  This is the first Macintosh to receive 128K ROMs.

The enhanced ROMs allow 800K floppy disks to be used.

Comes with two serial ports which do not support synchronous modems. Handshaking is not supported on output nor input.

The 512Ke does not come with a SCSI Port or ADB ports.

Sound output is mono.

Does not have an international power supply.