This is a HP-35 Red Dot which I owned at some time (but it is no longer in my possession).
The images here are shown as an example of how a HP-35 red dot looks inside because unfortunately this one has been opened prior to me being the owner. The calculator shows a number of differences when compared to later production units even some early 1143 series), like:
The charger connector has a differently shaped metallic piece.
The keyboard and the back of the calculator are kept together by 10 screws (8 in later versions)
The back of the calculator is made out of two different pieces of plastic
The screws that keep the calculator together are whitish; later models have black screws.
The battery door has a different label; notice the “model 03501A” compared to later (82001A).
Notice the metallic shield attached to the back plate above the components board. This has been dropped later.
Of course the red dot hole and the bottom label specific to the first 1143 series only.
Notice the charger model 03502A; later chargers are 82002A.
The soft leather case has a double stitch on the flap; later this was a single stitch.
The “5” key has a plastic dot on it; the dot exists for some of the later non-red dot versions (series 1143 and even some 1249).
The label at the bottom of the keyboard has the text “HEWLETT PACKARD”, later versions added the “35”.
The back square label for this calculator is NOT an original red dot label. An original label is presented here, but this machine had its label replaced at some point, probably when it received service.
The back square label for this calculator is NOT an original red dot label. An original label is presented here, but this machine had its label replaced at some point, probably when it received service.
Both the keyboard side connector (male) and the electronics board (female) are different than the later models. Later models have a “spear” design with two prongs on the keyboard which allows probably a better contact than a simple pin (as this one has). However on the electronics board later versions had simple holes with a metallic coating while this has real female contacts.
Tom Drewski had added an image of the hard plastic case that was used for the red dot version; because of the square shape of the AC adapter the location of the adapter in the case is slightly different for the first version.
Here are the images of the calculator proper. Clicking on the image will bring up a full size version.
