15 C.F.R. § 200.110
Schedule work assignments for calibrations and other tests will generally be made in the order in which confirmed requests are received. However, Government work may be given priority. On the regular services, the workload is usually such that the turn-around interval, between the date a customer's apparatus is received and the date it is prepared for return shipment, will be not more than 45 days. Some types of instruments may require considerably longer, particularly if their abnormal behavior requires reruns to check reliability. The customer who can spare the instrument for only a short time can usually arrange by letter or telephone call for shipping it to NIST just as the assigned starting date approaches. A notice will be sent acknowledging receipt of the customer's standard and/or purchase order. If both a confirmed purchase order (or equivalent) and the apparatus have been received, estimates of the completion date and the calibration fee will be sent upon request.
15 C.F.R. § 200.110