New stocks of Google Nexus 5 features larger speaker & microphone holes and fixed buttons
Google's Nexus 5 is without doubt one of the best smartphone money can buy. Still there are some issues which are clearly visible on Nexus 5. The initial stocks of Nexus 5 comes with smaller speaker and microphone holes and rattling buttons, which LG and Google has addressed, and has started shipping the updated Nexus 5, which features larger speaker & microphone holes and fixed buttons.
The user has posted some photos of new Nexus 5 alongside old Nexus 5, spotlighting the upgrades. As per the images, the power and volume buttons on the new Nexus 5 is no longer loose, and the speaker and microphone grill are larger than before, to give out better sound output/input.
To know whether you have the revised version of Nexus 5 or not, check the serial number of your Nexus 5 box. If the serial number starts with 311, then you are owing the Nexus 5 with upgraded hardware, else not. You can also check the speaker grill for confirmation.
Source - XDA Forum