Can I use a command to identify the modem?

Use the ATI commands. Here is the list for the ATIn commands for the MT128SMI:

Command: In
Function: Display Product Information
Unit: Decimal ASCII code
Values: n=0 - Product ID (e.g. 247)
n=1 - Firmware version number (e.g. 1.00)
n=2 - Product model
n=3 - Product features
n=4 - Date and time firmware was generated
n=8 - Current settings used by Windows for descriptor identification
n=9 - Product name
n=11 - Digital Port Connection Information
n=20 - Extended Product name
n=21 - Plug-N-Play string in HEX format
n=22 - Plug-N-Play string
n=24 - Boot code version
n=99 - Crystal frequency

Default: I0

Description: The In command displays specific product information depending on the value of n.