The growth of an interfacial perturbation after acceleration by a shock wave, known as the Richtmyer-Meshkov instability (RMI), plays an important role in the compression of an ICF target. Experiments studying the RMI are performed in a vertical shock tube by observing the growth of the interface between a pair of gases after acceleration by a planar shock wave. A near 2D, sinusoidal, membraneless interface is created in a shock tube by oscillating rectangular pistons at the stagnation plane between the two gases. The interface is visualized by seeding one of the gases with acetone, smoke, or atomized oil and observing the fluorescence or Mie scattering from a planar laser sheet. The results presented here span a range of Atwood numbers, 0.30<A<0.95, and shock wave strengths, 1.1<M<3. Numerical simulations of the experimental conditions are performed and compared with the experiments using the 2D hydrodynamics code Raptor (LLNL).