What was found
CREW REPORTED, IN CRUISE CONFIGURATION, SMOKE WAS NOTICED BEHIND THE GLASS OF THE HORIZONTAL SITUATION INDICATOR. SMOKE WAS CONTAINED INSIDE THE INDICATOR, BUT THE CABIN DID HAVE AN ACRID BURNING ODOR. UNIT CIRCUIT BREAKER WAS PULLED WHICH STOPPED THE SMOKE. CONTINUED TO FINAL DESTINATION WITH NO FURTHER ISSUES. MX R & R KI-525A HSI. ACFT RELEASED BACK TO SERVICE.