The Auto-Reflex P (export) and Autorex P (Japan) are a meterless version of the Auto-reflex/Autorex. As a result these are not capable of auto exposure and do not require any batteries.
In all likelihood, these were designed and offered as a less expensive entry level model, and perhaps to cater to customers who were uncomfortable with the "new technology" found in the Auto-Reflex with it's revolutionary "Auto Exposure" capabilities.
Today the A-R P and Autorex P are far less common than their "big brother" models. So now due to rarity they tend to sell for more than the higher end model with more features.
There was an accessory light meter available for use with the camera.