Apart from the aspect ratios of these two images which might suggest one format or another, there is simply no way to tell which camera was used. On the web, a picture made by a Minox or an 8x10 camera can look identical if they're posted at a typical 150 megapixel resolution. For a square negative (which is rightly assumed in the first case, I think) any of a number of cameras could have been used, i.e. Rollieflex or Rolliecord, Mamiya C series, Fuji, Kiev, and on and on. For the second, it's anyone's fair guess including the "rebate" that could have just been a PhotoShop border. (btw, my guess for the second image is 35mm, because it lacks the clarity of the square image, but that's just as good a guess as any other.) What matters is that if you like the look, try the camera, or at least the format you think made the image you like, and experiment. Good luck!