Determining the age of seaglass can be a complex process as it largely depends on a number of factors including color, thickness, and condition. However, there are certain indicators that can help.
For instance, the color of the seaglass can provide clues about its age. Olive green or brown seaglass usually comes from bottles produced in the late 19th and early 20th centuries. Clear or aqua pieces are often from jars or bottles made in the early to mid-20th century. Rare colors like red or yellow could indicate the seaglass is older, as these were less commonly produced.
The thickness and weight of the seaglass can also indicate its age. Older glass tends to be thicker and heavier than more modern pieces. If the glass is very thin and lightweight, it's likely a more recent piece.
Lastly, the condition of the seaglass can give you an idea of how long it has been tumbling in the sea. Older pieces are often more frosted and well-rounded due to the extended period of time they've spent in the water.
However, it's important to note that these are just guidelines and not definitive ways to determine the exact age of seaglass. The best way to get an accurate estimation is to consult with a seaglass expert or a professional in the field of glass manufacturing.