Now I have to correctly interpret your questions, as my interest/research covers the total 1932 to 1975 period.
By BLUE-COVER owners manual – presumably for a 1968 E-type you are referring to the handbook titled “4.2 ‘E’ TYPE AND 2+2 (LEFT HAND DRIVE CARS ONLY)”
This came in two different editions, E.145/1 and E.145/2.
AS far as I can establish E.145/1 was introduced for North American 4.2 E-types, both Canada and USA, from August 1967 onwards, so that includes what I call 1968MY USA Federal Regulation cars, but also same age Canadian Cars that were not built to the USA Federal Regulations regarding Emissions Control.
Its hard to be positive, but research to date suggests the mildly revised E.145/2 edition superseded from April 1968, and was issued to all the remaining (Series 1) 4.2 USA/Canadian production up until, again superseded by the Series 2 E-type, and its totally revised yellow-covered Series 2 Handbook.
So your 1E35152, built in 19 Feb 1968 will according to my research have the E.145/1 issue Handbook – I would be pleased if you would confirm that.
Now to the TAN-VINYL-WALLET.
These tan-vinyl-wallets were introduced from July/August 1961, but as with all other literature pack items, the design/style did evolve, and over the (Series 1) 4.2 period I have identified THREE major versions, that I call Type 1, Type 2 and Type 3, noting within each major version, there are minor variations, so a Type 1a, Type 1b, Type 2a and so on, just depends how exact you want to get, and although I am confident in my major versions demarcation points, I am less confident with minor versions which I consider manufacturing batch variations, rather than a deliberate design change.
The Wallet you illustrate with a straight-bottom edge to the tan-vinyl-flap is what I call a Type 1.
For your February 1968 E-Type I would expect to see the third-version, or Type 3.
See attached photo of Type 1, Type 2 and Type 3 Wallets respectively:-
Yours should be as the lower-example, with the key identifiers being the extended-tongue below the front flap, and having a TAN-coloured metal press-stud securing the tongue, noting that later Type 4 Wallets during Series 2 E-type era have a plastic-moulded in press-stud.
Now as per my earlier comment that pictured is what I call a Type 3b, which I believe is correct for your February 1968 E-type, but the earlier Type 3a sub-variant, was identical but with a Dark-Brown coloured press-stud.
Do you have any other of your original paperwork?
I found this 1968MY USA market period quite complex due to the changing support arrangements in USA, regarding other inclusions such as Service Voucher booklets, Dealer booklets etc, and although I am confident I did sort it all out accurately, I work on the principal of constant reinforcement as and when the opportunity arises.