MOD 9 digit serial number can be found simply by looking at the grey sticker of the battery pack.
Or by connecting your device to the Recon Uplink app
1. Power up your MOD HUD and plug it in to your computer
2. Log into Engage website engage.reconinstruments.com
3. Check the DEVICES > MANAGE DEVICES > SETTING GEAR (next to your HUD icon) for your 9 digit serial number
NOTE: You are required to register your MOD HUD on Engage website in order to see your HUD information.