The coil is an inductor. Indictors are most often used in the low-pass section of the crossover. The higher the inductance (measured in Henry units), the lower the frequency cutoff is.
The "1.75 A-50" is probably a resistor.
Most crossovers (for a multiple-driver speakers) use a combination of resistors, capacitors, and inductors. The funny thing is, all three of those components have have resistance, capacitance, and inductance -- a fact which must be taken into consideration when choosing components for crossovers.
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