It depends on the type of fork and the time period. I assume you're talking about a ashtabula blade fork since you mentioned a crown? The chrome fork crown on the blade fork started with the 1959 models. In the 60's for some time the dates were stamped on the inside of the left fork leg just above the axle slot with just two or three digits depending on the month. Later down the road I'm not sure if these forks had a date code on them, but some of the lightweight forks did. Starting with the 1966 models Schwinn upgraded the steer tube gauge so the i.d. got smaller and the stem diameter was smaller. I believe this is when the stems showed up with markings and possibly the forks too.