According to the datasheets, the peak forward voltage is 1.1.The maximum continuous forward current that this device consumes at any given time is about 1@Ta=55C.A DC reverse voltage less than 400 must be used for operation.
RL1N4004-T Features
the forward peak voltage is 1.1
RL1N4004-T Applications
There are a lot of Rectron RL1N4004-T applications of RF diodes.