How old is a marlin model 70 no serial number?

I can say that the Marlin model 70P(papoose) was made from 1986-1994.If you have the model 70PSS(stainless steel barrel,and nickel plated parts)these have been made since 1995.

The regular model 70 was introduced in 1983. At that time, .22 automatic rifles were required to have a serial number.