from openerp import models, fields, api

class factory_ref_stock(models.Model):
    _inherit = 'stock.move'
    _name = 'stock.move'

    @api.one
    @api.depends('product_id')
    def get_factory_ref(self):
        self.factory_ref = self.product_id.factory_reference

    factory_ref = fields.Char(string="Factory Reference", compute="get_factory_ref")