From which aircraft does this vintage altimeter come from?
What you have is a Kollsman C-12 altimeter manufactured by the Square D Company in Elmhurst, New York. The 50,000 FT marking below the Military Standard number means that the altimeter is accurate up to 50,000 feet of altitude but this number might far exceed the capabilities of a particular aircraft as it was universally used on many different types. The free of radioactivity sticker means that this instrument does not have the radium dials found on earlier models (common on WW-2 instruments) or, was later retro-fitted with a non radium face. Since you purchased this instrument in Thailand I am suggesting it came from a T-28 Trojan. The Royal Thai Air Force operated 120 T-28s from 1962 to 1988. The United States Navy ceased T-28 operations in 1984 but by then many of their T-28Bs  had been modified into "Ds" as counter insurgency aircraft and shipped abroad. Since the Thai Air Force recieved all their aircraft from America, there is a excellent possibility that your instrument came to Thailand either in a ex Navy T-28 or as a spare in a support maintenance package.