schema.org markup for a product with two prices: normal price and reduced price

I can't find the `itemprop`s for a product with two prices on schema.org. The types of prices are: - an old price - a new reduced price I can't imagine, that there is not fitting schema.org markup for this, but after a long search, I couldn't find the solution for this anywhere. Example HTML: ``` <div itemscope itemtype="http://schema.org/Product"> <!-- ... --> <div itemprop="offers" itemscope itemtype="http://schema.org/Offer"> <!-- What should I use for the old price? --> <div><span itemprop="???">4321</span> <span>€</span></div> <!-- Should I use "price" for the new reduced price? --> <div><span itemprop="price">1234</span> <span>€</span></div> </div> <!-- ... --> </div> ```