Same co., same stock, so you can sell it on either exchange.
But if you have a US funds acct. & sell it on the TSX your broker will charge you to convert the proceeds from $Cdn to $US. If you sell it on the US exchange you get $US. IMHO its better to stick with your "home" currency - hard enough to make a buck as it is without the fx considerations.
You won't lose anything selling it on the US exchange - the professional arbitrageurs on both sides of the border are all over these interlisted stocks fighting for any fractional fx advantage so the stock prices stay in synch with the fx rate.
Well done in any case - you probably bought it when the $Cdn was really cheap, maybe caught a split or two depending on how long "many years" is.
Thanks for the info. Yes, it has been through 2 splits. I have been what you might call truly long on this one and was mostly holding it for the dividends since they were annually greater than the price i originally paid for the stodk itself! With dividends on hold I am paying more attention to it.