The WaA number identifies the head of the military acceptance unit (Abnahmestelle) responsible for accepting this item as in agreement with the specification. Number 700 is also found on other Polte products from the 1939/41 time frame. When the man is transferred to another post, he takes the number with him. The WaA number of his successor will then appear on the accepted products. .
For diffcult to manufacture items, a lot (Lieferung) might be delivered in sub-lots (Rate). So the case is from lot 14, sub-lot c (Lieferung 14, Rate c) of 1940.
I am not an expert in this type of ammunition and cannot say whether the WaA stamp documents the acceptance of the case or the entire cartridge.