'Stereoscope,<br />bifocal lens,<br />x-ray tube'
bifocal lens
INVENTED FIRST: Stereoscope,<br />bifocal lens,<br />x-ray tube
Stereoscope,<br />bifocal lens,<br />x-ray tube
Stereoscope,<br />bifocal lens,<br />x-ray tube
INVENTED FIRST
bifocal lens
INVENTED FIRST