A vibrating organ pipe has a fundamental frequency equal to 200 Hz .

The organ pipe can be open at both ends or closed at one end.

For an open organ pipe, the frequencies of harmonics are given by $f = n f_0$, where $n = 1, 2, 3, \dots$
The fundamental frequency is $f_0 = 200 \text{ Hz}$.
The frequencies are $200 \text{ Hz}, 400 \text{ Hz}, 600 \text{ Hz}, \dots$
The first overtone is $400 \text{ Hz}$ and the second overtone is $600 \text{ Hz}$.

For a closed organ pipe, the frequencies of harmonics are given by $f = (2n-1) f_0$, where $n = 1, 2, 3, \dots$
The frequencies are $200 \text{ Hz}, 600 \text{ Hz}, 1000 \text{ Hz}, \dots$
The first overtone is $600 \text{ Hz}$.

Thus, the first overtone could be $400 \text{ Hz}$ (if the pipe is open) or $600 \text{ Hz}$ (if the pipe is closed).
In both cases, $600 \text{ Hz}$ is an overtone (second overtone for open pipe, first overtone for closed pipe).