What is a Martin D45 guitar serial number 500303 worth?

According to past listings, a Martin D45 guitar with serial number 500303 could fetch anywhere between $12,000 and $18,000. Please note that the actual value may differ depending on various factors such as the guitar's overall condition, provenance, and current market trends. For a precise valuation, I recommend consulting with professional musical instrument appraisers or reputable vintage guitar retailers.