Evaluation of type B uncertainties

The ISO Guide states that

For estimate $x_i$ of an input quantity^6.3 $X_i$ that has not been obtained from repeated observations, the $\ldots$ standard uncertainty $u_i$ is evaluated by scientific judgement based on all the available information on the possible variability of $X_i$. The pool of information may include

• previous measurement data;
• experience with or general knowledge of the behaviour and properties of relevant materials and instruments;
• manufacturer's specifications;
• data provided in calibration and other certificates;
• uncertainties assigned to reference data taken from handbooks.