2 Pack 09985 Pressure Canner Sealing Ring & Overpressure Plug for Presto 01751 01781 01784 01745 01755 Pressure Cooker

Model # 01784 is mentioned in the title, but not in the product details. Confusing: is it or is it not suitable for this model?

Do you get 1 or 2 seal gaskets? the pic shows two.

I have model 0178001. yup, its that old (1959). works great, except now i need a new seal. will this fit?

How long do these last until they need to be replaced? Also, if I order these to have on hand as spares, will they age and get brittle in storage?