The microscope stand - the entire instrument without the magnifying lenses and other interchangeable accessories - are quite varied and have evolved over the years so they help date an instrument. By the mid to late 1800s when microscope production and use began in earnest, two major types of stands dominated the market. One is the Continental stand, with the reputation of a practical research tool, manufactured mainly in Germany and include the Zeiss jug-handle stand, introduced in 1898. The other is the English stand, which is generally larger and more elaborate, delicate and complex with a plethora of accessories. Microscopes have continued to evolved in design, components, optics and other features related to progress in metallurgy, optics, manufacturing and electrical technology, but until the 1940s, some stands had remained remarkably similar in appearance for over 60 years. Binocular instruments became the norm during the 1930s, and by the 1940s variable illumination options included both substage transmitted light and overhead reflected light from the touch of a button. In the 1960s advances in lens technology included surface coatings and flat-field optics.