In the 1960s Dr. David Littmann M.D.created what has become one of the most iconic models of stethoscope. His creation named the Littmann Cardiology became the gold standard for the modern stethoscope. Littmann and a partner formed Cardiosonics Inc to sell and market his product. The company was soon purchased by 3M which continues to manufacture and distribute a namesake line of Littmann stethoscopes. 3M also produces a large variety of other healthcare products. One benefit of being a product line of 3M is that there is a large corporation backing the end consumer device. This means strong customer support and ultimately peace of mind knowing that your stethoscopes warranty policy will be honored.
From their website:
Numerous 3M innovations such as tunable diaphragms, Ambient Noise Reduction, and Bluetooth® stethoscope connectivity, have extended the capabilities of Littmann stethoscope far beyond Laennec’s (and perhaps Dr. Littmann’s) wildest dreams. Littmann stethoscopes have become the gold standard by which all other stethoscopes are judged.—the brand that delivers superior acoustics, innovative design, and exceptional performance.
If you have time check out the Littmann education resource center which includes links to their free app that you can use for learning how to listen with a stethoscope.