My guess is Item Code 5 (1976) was the first release of those tables, but I cannot confirm that.
Item Code 5 are Ready Reference Charts, which were of course the predecessor of the Ready Reference Book.
Dated 1976
But in the three pictures/scans offered for each printing of them on the Judges Guild pages I do not see the Weapon Priority Chart.
http://www.acaeum.com/jg/Items0005-7.html

The Judges Shield (1977) includes the Weapon Priority Chart on one of the sides of one card/page.
The site states they are Sheets (thin paper?) but mine are thick double sided heavy card stock... real thick.
Item Code 28
http://www.acaeum.com/jg/ModPhotos/Judg ... tion1.html
http://www.acaeum.com/jg/Item0028.html

The Loose Ready Reference Sheets also has the Weapon Priority Chart.
(Specifically Sheet J - 5)
Item Code 14, which was included with Installments J, K & L
Dated from 1977
Cover Sheet for the Ready Reference Sheets package
http://www.acaeum.com/jg/ModPhotos/Read ... pe1st.html
Sheet J - 5
http://www.acaeum.com/jg/ModPhotos/J5RefSheet1st.html

I can confirm the two Items Coded 14 and 28 DO include the Weapon Priority Chart as I have copies of both of them.
Plus the scans/pics on the JG pages confirm them as well.

J 1-4 are Dungeon Maps for the Thunderhold Package, or Installment J.
One would think J 5 came at the same time or after those Dungeon maps.

That said, I suspect you are right.
The Thunderhold Installment also includes J-5, and it is dated 1976, though it has no item number...

Initial Issue (Judges Guild Journal) dated October 1976 has a booty list (10 is the highest Item number) which does NOT include Installment J, J - 5, or Thunderhold.
Items 9 and 10 were future products (Judges City Map and Guide to the City State, 40 page booklet).

Journal K (double sided single page legel sized newsletter) is dated FEB/MAR 1977 and Installment J is shown on the booty list, the highest Booty List item is 20 for this issue.

I do not have a copy of Journal J, but it was published for the period of Dec 1976/Jan 1977.
I am sure that it also includes a booty list (Site says numbered to 17).

Journal K shows GL Booklet J (12 pages) and Ready Ref Chart J-5 as Item 16 , then I suspect it was also included in Journal J's Booty List.

From the data we have listed here it seems likely to me that J 5 came out in late 1976; November, or December to be precise.