[TenTec] Triton V & Omni Series - Tens Green Digit

[k7mks at comcast.net]

The green digit on my "new to me" Triton IV (Model 544) is usable but not as bright as the other 5 red digits. I've also noticed that many of these models that appear on auctions suffer from the same problem with some being difficult to decipher. With the number of "dull" green digits out there I'm wondering if this a normal characteristic or perhaps a result of aging in these two or perhaps other TenTec models The lack of posted comments leads me to believe that this is normal. 
Your ideas will be welcomed. 

73 joe k7mks