Welcome to the Forum! You have a S&W Model 10-6, aka .38 Military & Police. Before 1957, these revolvers were known simply as .38 M&P, but in 1957 S&W began using model names and these became the Model 10. The 10-6 version was introduced in 1962, and the "D" s/n number prefix began in 1967. The s/n of your revolver indicates that it was manufactured in 1973. The finish on your 10-6 is a little rough and worn, and the ill-fitting stocks (grips) are aftermarket (they would have originally been checkered walnut magna stocks)...both issues affect the value. There were literally millions of .38 M&Ps manufactured over many decades, so your revolver is not rare or valuable. I would think that your 10-6 in its current condition would be worth maybe $300-$350.