In the context of developing a hadron calorimeter with extremely fine granularity for the application of Particle Flow Algorithms to the measurement of jet energies at a future lepton collider, we report on extensive tests of a small scale prototype calorimeter. The calorimeter contained up to 10 layers of Resistive Plate Chambers (RPCs) with 2560 1 times 1 cm2 readout pads, interleaved with steel absorber plates. The tests included both long-term Cosmic Ray data taking and measurements in particle beams, where the response to broadband muons and to pions and positrons with energies in the range of 1 - 16 GeV was established. Detailed measurements of the chambers efficiency as function of beam intensity have also been performed using 120 GeV protons at varying intensity. The data are compared to simulations based on GEANT4 and to analytical calculations of the rate limitations.