.32-44 is good to go for antique, the only stipulation is the age of course. Very few guns were made in this caliber across the entire run of the No. 3 so it would be wise to have a RCMP letter to be sure
The cartridge itself is completely unique, much like the .320 S&W revolving rifle cartridge which also falls under antique status
With regards to the .32 M&H aka the .32 H&R, it is still very difficult to get into these unless you have a 12(6) and make the case for deregistration for one you already own OR buy a lettered gun from someone who has already done this, if you try to get it across the border without already being lettered they may still turn it away or hold it in customs jail, at the most extreme requiring a physical visit to get it back
Pretty sure I know which dealer you are speaking of and they bring in excellent pieces, this one being no exception but it has a price to match - if one could justify the purchase, it looks to be a very nice example and would still serve as a very good target gun if proper care was taken about the ammunition