Help Identifying Capacitor
That looks like 100 nF, 1 kV.

The value is indicated by "104".  That's a decimal floating point format commonly used with capacitors like this.  The first two digits are the value in pF, and the last digit the power of 10 to multiply the value by.  "104" therefore means 10 x 104 pF = 100,000 pF = 100 nF.