The dragon is a symbol of the natural world, adaptability and transformation and is one of the Twelve Symbols of Sovereignty, representing the emperor. The combination of this symbolism with the auspicious long and shou characters appears on many works of art that the emperor distributed as gifts.
The presence of mask-and-ring handles and the accomplished carving of the overlay suggest that this bottle was made at the Palace workshops. For a discussion on the small masks with circular rings on Imperial snuff bottles of the mid-Qing period, see Moss, Graham and Tsang, The Art of the Chinese Snuff Bottle. The J & J Collection, no. 347.