The Sigma SE-19 is an acoustic guitar used by Prince on the Sign O The Times, Lovesexy and Nude tours. Sigma were an offshoot of the Martin brand built in Japan. Despite resembling a Martin, the design of the guitar is unique to Sigma. It was played by Prince for the performance of Forever In My Life in the Sign O The Times movie. It also appears in the Glam Slam video. It has a silver heart behind the bridge.
A similar guitar built by Washburn is now in the Sign O The Times room at Paisley Park. This is not the same guitar, but is instead the guitar from the 7 video. The SE-19 is in the collection at Paisley Park