New-Old ND 0.6 filter
I just purchased and 49mm ND .6 from online and when it arrives I could tell immediately that this filter is almost as old as I am. The box has a product date of 12 Feb 1987, and it looks like it. My question is, what is the main difference if any between new Tiffen filters and ones made 2 1/2 decades ago. Could this things be worth more than a new one? Glass quality improved? ect.
Thank you in advance for any help you all will give me.