I think it was made in early 1990. From my N-frame s/n collection:
BEN67XX …………. Dec 14, 1989 (M625-3 .45A 4“) RB 100925 1pc-box 9348
BFA68XX …………. April 19, 1990 (M610-0 6.5“) RB 103576 nils 1pc-box 0109
I don't have a N-frame BEZ but it should be right there before BFA. Was wondering if it had a special s/n which might help nail it down as a limited edition, special run, Lew Horton kind of thing. 1990 was right in the heart of S&W's famous "Gun of the Week" period. In that time frame they put out lots of interesting small run stuff, to my knowledge, a lot of it is not well documented.
I do have a BEZ in my J/K/L-frame collection. N-frame s/n's typically precede them by a few weeks or months.
BEZ17XX …………. April 24, 1990 (M631-0 2“ 32M) RB nils FS 103664 1pc-box 0114
BEZ29XX …………. June 19, 1990 (M631 4“ .32M) RB AJS 1pc-box 0170