A mechanical device including a crankcase and reservoir plug suitable for detecting the quantity of lubricant is disclose. In an aspect, the reservoir plug is configured to permit observation of the interior of the plug/crankcase in order to observe the level of contained lubricant. The drain hole for receiving the plug is disposed to encompass the range between the maximum acceptable lubricant level and the minimum acceptable lubricant level. The plug may include a main body portion and transparent portion for permitting observation of fluid, disposed on a second side, from a first side of a sealing interface.