There are significant differences between D-Day (1961) and D-Day (1965). The physical component changes are significant.
1. BOX COVER:
1961 = "Now YOU change World War II History in this realistice Tournament GAME by Avalon Hill. Adult. 12 Years & Up"
1965 = "Now YOU change World War II History in the realistic INVASION GAME by Avalon Hill. 12 Years & Up"
1961 = Botom right quandrant has 13 locations for Allied Corps Substitute Counters. This is just under the Bay of Biscay invasion instructions.
1965 = The locations for Substitute Counters do not exist, they have been removed from the map.
1961 = To the right of the Allied corps locations is the logo "D-DAY* Realistic World War II Game by THE AVALON HILL COMPANY Baltimore Maryland. Copyright 1961 - The Avalon Hill Co. Printed in U.S.A. *T.M. Reg. App. For (This is all in BLACK PRINTING.)
1965 = Where the corps locations used to be is the logo "D-DAY THE AVALON HILL COMPANY BALTIMORE, MD Copyright 1961 - The Avalon Hill Co. Printed in U.S.A. (D-Day is in red printing; rest of text is in black. Tradmark data is deleted as well)
1961 = The mountains are light brown in color and Switzerland is made of gray hexes with the name imposed over the areas.
1965 = The mountains are flesh or yellowish tan in color and Switerland is now a gray blob, with very poorly drawn black lines around the blob.
Hexes are deleted where the name is located. (it looks like white-out was applied to an old map and reprinted poorly)
1961 = no map grid numbers and letters to locate specific hexes
1965 = map grid numbers and letters to locate specific hexes (A-UU and 1-44)
1961 = Just above Switzerland are 3 locations to place German Corps Substitute Counters.
1965 = German corps locations deleted. Gray blob of Switerland now in that area.
1961 = 4 hexes betwen the Rhine and first Island in Holland are water hexes
1965 = 4 hexes between the Rhine and first Island in Holland are land hexes
1961 = River between Holland and Germany is printed Ijessel Rhine
1965 = River between Holland and Germany is pinted Ijessel
1961 = Holland Dyke instructions state: "Units may cross but not attack"
1965 = Holland Dyke instructions state: "Units may cross Dyke. Attack while on Dyke not allowed"
1961 = West wall hexes pink color
1965 = West wall hexes red color
D-day 61A and 61B have 4-page rule booklets,
D-Day 65 consist of a 4 page booklet for the basic game plus a 12-page "Battle Manual" containing rules, examples of play and, commentary. D-Day 65, however, incorporates significant rule differences from its predecessor.
The object (Allies enter and remain in Germany in force before the 50th turn) and operational mechanics (select one invasion area among 7, invade and get ashore in strength, then advance to Germany -- possibly aided by a second invasion) are largely the same as in the predecessor. Game tactics in general are the same as in all AH land wargames up to this date (rigid ZOCs, same CRT, try to get 3:1 attacks, try to surround defender with ZOCs, "soak off"if necessary). There are some major rule differences that have a major effect on game play. Among the changes are:
1. A rigid 17-hex supply line length is imposed on the allies (rendering use of S France as an invasion area bizarre if not, as some claimed, totally useless).
2. The same CRT is used as in all AH games of this period, but low odds round in favor of defender instead of toward 1:1 as in the 1961A games.
3. River defense bonus applies only if all attackers attack through river hexsides (in the 61A version, the bonus also applied if attacker has moved 1 hex across a river into the defender's ZOC). River defense deployment is considerably different as a consequence.
4. The tournament game added "strategic air attacks" to the Allied arsenal: 8 attacks per game in each of which (usually) 2 or 3 German divisions would be destroyed. (Some refer to these, sarcastically, as "nukes").
5. Allies now get 2 replacement points/turn starting turn 9 (formerly none), but Germans can no longer replace HQ or static divisions (leading to shortages in the number of units on the board later in the game).
6. Units in fortresses now are always in supply.
7. Retreat path of 2 hexes through Mtns now is prohibited, but retreats across rivers are allowed (as in 61A, but unlike 61B).
This is not an exhaustive list: there are numerous other minor rule changes and clarifications in D-Day 65. By the time D-Day 65 came out, the Avalon Hill General was in publication and there were frequent "official" changes to the rules promulgated in a question and answer section of the General, especially as regards details of supply .
1961 - "Time Record Card" has two-sided turn track with 50 games on the top and 50 game weeks on the left. 100 games can be played with this track.
1965 - "D-DAY TIME RECORD CARD" has two-sided turn track with 10 games on the top and 50 game weeks on the left. Game column now has accumulated replacement tracks for allied and german to the left and right of the turn column. Solid black printing for those turns when replacements can not be accumlated (turn 15 for germans and turn 9 for allies). 20 games can be played with this track.
1961 - 2 yellow cards with 4 charts: a. Combat Factors (terrain effect chart w/examples; b. Examples of play c. Order of Battle with unit ID legend; d. Unit symbol explanation.
1965 - 1 white card with 2 charts: a. Order of battle and b. Examples of play.
Any of the versions are playable (if players can agree on a few rule interpretations or fixes) and even today are enjoyable, so long as you are not expecting a 2000-era game system in a 1965-era game.
Source: E_T_Lee, personal comparison of components and rules
Source: SJ Rauch: personal comparison of components and rules for 1961 and 1965 editions (Sep 2017)