yes, but it says it has 5gb/s in the usb details in hardware, on my mbpro :S
That is USB3's interface speed. You won't get that speed out of a spinning hard drive.
The absolute max speed you're likely to get out of a SATA spinning disk (like, say my 3.5" western digital black) is roughly 100 megabytes/sec or so.
Also MB/sec (bytes) vs Mb/sec (bits).
If you were running USB 2, that is 480 megaBITS per second link speed, in reality nearer 320 megabit throughput. If your drive was running at USB2 speed you would be getting less than 40 megabytes per second. To convert bits/sec to bytes/sec divice by 10.
Yes, there are 8 bits to a byte but there's a bit of signalling overhead and divide by 10 is roughly accurate once that is taken into account and easy to calculate in your head.
You're getting nearly double that.