I've attempted several times to search this forum for identification of the dash/ number nomenclature for the 617 Smiths. What are the distinctions between a 617-2; 617-4; and 617-6. Is there a reference source that denotes these distinctions? Thanks in advance. Drew

Welcome to the forum.
Best resource I'm aware of is the SCSW 3rd Ed.

But in attempt to answer your question, 617-2 had 10-shot aluminum cylinder, 617-4 had 10-shot SS cylinder and MIM internals, 617-6 has the internal lock.

No dash, Product code # 100568

-6, Product code # 160578

A list I put together based on the Standard Catalog of Smith & Wesson and my own observations...

Model 617 K-22 Masterpiece Stainless Full Lug, .22 LR

-n 1989, Introduction, 4, 6, & 8 3/8-inch barrels, full lug. One-piece cardboard box.
. . 1991, Small run of 4 & 6-inch produced without full lug, for Ashland Supply.
. . 1993, April, transition begins from wood Combat Stocks to Hogue neoprene grips.
-1 1993, October, drilled & tapped for scope base, new rear sight & extractor.
. . 1994, September, Hogue grip transition complete.
. . 1995, Mid-year, shipments transition to blue plastic case.
-2 1996, 10-shot alloy cylinder, glass-bead blast finish, round butt, MIM thumbpiece.
. . 1996, June, Uncle Mike combat style grips seen in use.
. . 1997, October, 10-shot stainless steel cylinder replaces alloy cylinder.
-3 1998, 6-shot new style frame, delete serrated tang, MIM trigger, new lockwork.
-4 1998, October, 10-shot new frame, delete serrated tang, MIM trigger, new lockwork.
. . 1998, Small run of 10-shots 4-inch without full lug, SCSW calls it “stovepipe” barrel.
. . 1998, October, Hogue grips again seen in use.
-5 2001, 6-shot Internal Lock System (ILS).
-6 2001, 10-shot Internal Lock System (ILS).
. . 2002, Ceases production of 8 3/8-inch barrel length.
. . 2003, New style star extractor.
. . 2006, January, shipments transition to a new style blue plastic case.
. . 2011, November, S&W proprietary synthetic grips in use.

__________________
~ S&W aficionado in training ~

Question answered in full. You're a good member there Kernel.