The valuation of any property not specifically described in §§20.2031-2 to 20.2031-8 is made in accordance with the general principles set forth in §20.2031-1. For example, a future interest in property not subject to valuation in accordance with the actuarial principles set forth in §20.2031-7 is to be valued in accordance with the general principles set forth in §20.2031-1.