F15 lamps are usually 18", which would be 1.5ft. A 1.75ft lamp would be around 20", which is definitely not a standard length.
actually 1.75ft/20 inch is quite a standard tube length
its just the tube that is that long, is somewhat uniquely one of the few straight fluorescent tubes thats not refered to by its length and when its length is given its given in milimeters only,
that tube being the F13T5 which is 525mmm long aka 1.75ft or 20 inches (roughly)
for whatever reason rather curiously that tube was never adopted into the normal inches measurement that tubes have
which I am pretty sure thats what this both by the description of length and the style of tube/end cap fitted (the relatively deep caps vs tube diameter etc) I am pretty sure its some sort of F13T5 light fixture and tube (with the same style of Lamp holders you find in old GEC 2xF8T5 bulkhead lights)
