842 Town Plan
General Information
The following information has been collected from original newspapers, catalogs, and magazines, some of which are freely available for reference below. The rest can be found in the site’s gallery. No aggregate catalogs (BrickLink, Brickset, etc.) were used.
Instructions: H-2528
Advertised Part Count(s): 842 pieces
First Year Confirmed Available: 1969(USA)
USA Only.
Most Likely Retirement Date: 1970(USA)
Last Year Seen Available: 1970
Aliases: Unknown
Note: Neither Sears catalog assigns the set a proper name. In light of no usable name to refer to the set, I've settled on using the colloquial name for the set. Note that it has been applied retroactively and does not appear in any Sears catalogs.
Retail Price(s): $17.99-$18.99(USA)
Rarity Score(Index): 6/7
Known Box/Packing Variants
There may be different versions of the outer box across 1969-1970(it only ever came in a plain box, but numbers and such could deviate), but there are at least two known versions of the inner tray. There's currently not enough information to extrapolate which belongs to when and set them on a timeline.
The more common version uses the single piece gray tray:

The other uses a drawer with paper/plastic inner trays:

Box/Overview
The 842 Town Plan is an odd duck, to say the least.
It's no secret Sears tended to get interesting exclusives, what with the 371 Motorized Truck Set, the 118 Motorized Train, the 536 Designer Set, etc. But the 842 is interesting in that it does not have a comparable alternative on the market at the time. The 371 had the 310, the 118 had the 119, the 536 was like any other basic set... why was the 842 created?
The 842 Town Plan appears in 1969—several years after the end of the town plan era. All pre-existing town plan elements(road signs, gas pumps, etc.) had already been retired and liquidated(in 1968 via the 704). The only thing that remained were the 1:87 cars, though they evidently lasted until late 1970, as some 157 Auto Transports have been found with genuine LEGO cars.
Maybe it was something as simple as Sears requesting another exclusive set(though how it was brushed off in the 1970 catalog is a bit odd), or maybe it was an attempt to burn through remaining 1:87 inventory as well as oddball parts(as the 842 makes unique color choices), hence the sudden 1970 only appearance of the 157 Auto Transport. That'd help explain why this set contains the 4x8 rounded plates—an element that disappeared from the North American LEGO system in 1965 with the retirement of the 1961-65 supplements.
No one really knows.
Contents
The set came with enough elements to construct the intended town model.

Most examples will be found with very brittle blue plates and will not be able to be constructed.
To substitute the original Esso accessories, as those were long gone by now, the set uses a Shell sign and gas pumps.
It also came with an exclusive town plan board based on the original 725's layout, which at least corroborates this is a Samsonite original and not a reuse/repackaging of something else:
A comparison just for fun:
The 842's board was never sold separately. It is one of the hardest elements from this set to source as it does not say LEGO anywhere on the board and most people would not assume it to be LEGO. The back is blank: