Which RT series is this MSR attachment designed for, and does it include a fingerprint reader?

It is designed specifically for the 15.6-inch RT series, and it is a USB attachment without a fingerprint reader.

What type of magnetic stripe reader is the Posiflex RA1011, and is it encryption capable?

The Posiflex RA1011 is a 3-track magnetic stripe reader, and it is encryption capable.

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Posiflex RA1011, MSR Attachment, 3-Track Encryption Capable, USB w/o FP Reader for General Payment Processors, for RTxx16 - RA10111000 - OEM