Single Contact Morse Code Key Base_Octagonal these concavity microscope slides hold

these concavity microscope slides hold liquid samples for hanging-drop preparations and observation of specimens in suspension

Eight 15 x 10 x 10cm pinhole boxes

Plated spring arm with press knob and a single contact stud

Eight aluminum-shank tuning forks tuned to scientific pitch (C4 = 256Hz) and ranging from 5 9/16 to 7 1/8 inches

measuring period under different loads to isolate mass from weight

Single Contact Morse Code Key Base_Octagonal these concavity microscope slides holdPlated spring arm with press knob and a single contact stud, configured to make and break a circuit at the rhythm of a Morse code transmission for telegraph history demonstrations.