When the two men are discussing "Voltones" while holding Smith and Will, the Robot approaches. One of the men shoots the Robot, striking him just to the right of the illuminated voice-plate leaving a sizable mark. Seconds later, after the Robot has incapacitated the men there is no mark whatsoever.
Numerous times in Season One the year of the Jupiter 2 liftoff is stated as 1997, therefore nothing in 1947 would be mysterious to any of the crew as Dr. Smith would have been born around this time and Maureen and John just a few years later. The phones and the cars would not be strange museum pieces. In theory, John and Maureen could have conceivably contacted their own parents.
Near the end, Craig is on the phone and identifies his town as "Manitou Falls" - but throughout the story it has been called "Manitou Junction." He clearly got it confused with "Chickasaw Falls" - the town Dr. Smith claimed he was from.
When the Jupiter 2 was landing, a circle marking the landing area was seen, but after that there was no marking ever seen again.
As Maureen and the girls are investigating the area after initially landing, they come across an office area and enter the building. They find a telephone and lift the receiver. None of them seem to know how to operate it or know what it is, although Maureen says that she has seen them in museums but is unfamiliar with them. However, in the Pilot it is clearly seen that telephones were still commonly used at Alpha Control during routine communications. Also, in #1.15; Return From Outer Space, when Will returns to Earth with the help of an alien matter transfer machine, it is one year after the J2 departure. Telephones are commonly used throughout the story and are seen to be of an older variety. A telephone operator is even employed. Will even tries unsuccessfully twice on two separate occasions to get the operator to place a call to Alpha Control.
When John Robinson and Major West find the car in the barn the radio is turned on. The voice identifies the date as Saturday, October 17 1947. October 17 1947 was a Friday.
Dr. Robinson mentions that the first moon landing was in 1970. The first moon launch was in July of 1969.
After coming out of hyper space John, Don and Dr. Smith look out at planet Earth from inside the J2. Also visible is Saturn, Jupiter and some other planets and/or moons in our solar system. Not all of these other planets would be visible to the naked eye simultaneously as shown.
Judy Robinson's hairdo changes just after the Jupiter II lands - notably when she is captured by Craig, it is now shoulder-length and straight, but before landing, her hairstyle is curlier. It resumes its curly aspect after John and Don rescue her - without comment or explanation.
If the Robinson's didn't change into their space suits, then they would have looked like humans to 1947 earthlings.
There is a perfect circular landing pad marking where the Jupiter 2 lands. Since no one of that time would know of the Jupiter 2 this shouldn't be there.
When the crew lands in the year 1947 at an American production facility for radio and furniture cabinets, a huge object is seen in the background. It is covered by a large, seamless plastic sheet, and held down from the wind with lumber. Polyurethane plastic sheeting had not yet been developed: in nineteen-fifty-three, a catalyst was found and applied, and new plastics such as sheet form were developed, and became common. The unknown object was most probably hidden as it did not relate to the time and location sensitivity of the town portrayed.
After passing through an anomaly of time and space, the Jupiter II arrives in Earth orbit - 50 years in the Robinsons' past. It is made clear that the family cannot remain on the planet, but there is no discussion about how the Jupiter II will return to its original time and place. At the end of the episode, the ship simply flies away from the Earth of 1947.
They are piloting a space ship capable of navigating to another star system, yet they are unable to locate where they are on Earth and fly it to a known location, such as where Alpha Control is supposed to be. Instead, they just drop into the parking lot of a production warehouse in Michigan.
When Dr. Maureen Robinson & the girls are confronted in a shack by a "candlestick" telephone, she is too mystified by the contraption to be real; she professes having seen it being used but couldn't figure out how to use it, this despite the events they were only 2 years removed from their Earth launch. As such, Maureen couldn't have been past 45 at that time (born at most in 1952, only 5 years past the timeframe they found themselves in), & when she lifted the receiver and tried talking past the weird noise that clearly wasn't a dial tone, she should have recognized the sound since it was used until at least 1980 - only 17 years before they left, roughly when Judy would have been born during Maureen's 20s.
Several characters speak with a "southern" accent although they are in Michigan.
When they reach Earth orbit and claim they can't reach Alpha Control, they should have monitored other radio frequencies.
First, to ensure someone was really there.
Second, to locate who to contact and find what is going on.
Third, to find air traffic control frequencies, which would be important for flying into US air space even in 1999 to prevent collisions with other aircraft.
Fourth, to find air defense frequencies to establish contact to prevent being shot down.
Any pilot would have known to do this.