[![enter image description here][1]][1]

From the Chart Supplement it seems 1O5 is unattended for all of this requirement: Mon-Fri 10 AM to 4 PM. It's likely the service in on-demand by calling up ahead.

    1O5: Unattended
    SIY: Attended Sun–Fri 1600–0100Z‡

While for SIY the attended duration is 9 AM to 6 PM, the FBO may have intermittent or seasonal presence.

The Chart Supplement does not have to mention such irregularities according to [IACC 8][3] section 3.1.5.5.4.5:

>The following type data shall NOT be published in the SERVICES and REMARKS sections:

>>g.  Temporary shortages of certain types of fuel, starting equipment, or other aircraft services;

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I got the chart supplement for both airports from [skyvector.com][4].


  [1]: https://i.sstatic.net/t0663.png
  [2]: http://www.airnav.com/airport/1O5?pagewanted=all
  [3]: https://www.faa.gov/air_traffic/flight_info/aeronav/iacc/
  [4]: https://skyvector.com/airport/1O5/Montague-Yreka-Rohrer-Field-Airport