You are asking exactly what Im sorting out at present, I went to see a NAV mount today that looked exactly like this one in your picture and my 660 wouldn't fit. The mount was for a Zump 550. looked very similar but the 660 wouldn't go in .
If the mount on your bike is for Nav lV or V. The 660 will fit.
Looks like a Nav lV mount to me, same as mine. The 550 connections are near the bottom of the device.
You are asking exactly what Im sorting out at present, I went to see a NAV mount today that looked exactly like this one in your picture and my 660 wouldn't fit. The mount was for a Zump 550. looked very similar but the 660 wouldn't go in .
Then the one you tried wasnt like the one in the photo.
The mount shown in the pic - takes the NAV 4, NAV 5 and Zumo 660. (but - none of the 4 buttons on the mount have any functionality when a 660 is in the mount)