It was fluoroscopy (an Xray 'movie' rather than an X-ray film as such). Our resident imaging expert, @Cunobelin, can explain why it was a very, very bad idea to have fluoroscopy in shoe shops.
Basically unregulated xray machines that fired a beam that was less filtered than today. Even if it was working properly, by looking into the system you put the sensitive eyes into the direct beam.
There are probably quite a few people walking around with the long term effects of high doses or radiation due to these machines
Mind you it could have been worse.
In the light of today's knowledge you would probably not have marketed these either