536 Designer Set
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.
Note: The 536 used the H-2308 only for 1967.
Advertised Part Count(s): 536 pieces
First Year Confirmed Available: 1967(USA)
Sears Exclusive, USA Only.
Most Likely Retirement Date: 1971(USA)
Makes its final appearance in the 1971 Sears Christmas Wishbook and would not have been produced after the 1971 loss of the LEGO license.
Last Year Seen Available: 1971
Aliases: Designer Set, 49-4419, 49-16094
Retail Price(s): $9.97(USA)
Rarity Score(Index): 3/7
Known Box/Packing Variants
The 536 Designer Set is both fortunate and unfortunate, in that many box variations exist and are documented, but it is difficult to place them in a simple timeline.
There are several versions of the shipping box, with or without the manufacturer number. I'm not currently aware of any 536 boxes with the 1970+ updated 49-16094 catalog number on the side flap, the examples below all have 49-4419:


The following two examples should be from 1970. I say "should be" as they might be overstock from the 1969 season that needed an updated catalog number for 1970, but the "Some parts...manufactured in Denmark" sticker indicates they left Samsonite's factory in the 1970 season.

Around 1968-69, a colorful box was released(this evidently did not replace the above sets sold via catalogs, at least not initially):
And in ~1970-71, the box was updated to have "Some parts...manufactured in Denmark" printed directly on the box and tabbed ends:

The tabbed ends meant the end of the 536's unique drawer, reverting to a generic drawer. This updated version would've been used for catalog sales as well for at least 1971, as no mailer box should exist (using the 244 Explorer Set as an example, which corroborates that colorful boxes were used to fulfill catalog sales ~1971).
Box/Overview
The 536 Designer Set was released in 1967, following a complete restructuring of 1966's exclusive line of sets for Sears. Its DNA can be found in the 565-piece set from 1966, mainly via the similar box sizes and pieces counts. The big difference was the inclusion of a 1:87 vehicle, which were no longer being sold individually for the US market.
While we can show it took until late 1968 for the mailer version to get a new pamphlet(via the form numbers and we now have the 1967 version), it is much more difficult to determine when the 536 got its colorful box. I'm assembling a dedicated article on the topic.
For now, we'll examine the box. One thing I want to note is that the image of the house is superimposed on the front. The child is not physically playing with that house model as there are no shadows, and the depth/angle is off:
This drawer was used in both the colorful box and the mailer box from 1967-70. It stopped in 1971 as the colorful box had switched to tabbed ends:
Contents
The 536's inventory of basic bricks likely varied between 1967-71. The set is known to have contained any of the six 1:87 Vehicles available in the US, though ~1971 copies will likely be missing the 1:87 vehicle/garage and will instead include the standard garage kit and a Minix car. The set should contain trees, examples from ~1970 will have trees with feet:
This 1970-71 example is an oddball as it contains both the 1:87 garage/car and the standard garage. I assume it to be a matter of mixed collections and not how the set came originally, but who knows:
