Mercer indicators, marketed for the UK, are no longer available. They were made in Swizerland and were identical to the Compac indicators except for the brand name on the dial. The dial often, erroneously, read "England" which can lead to confusion.
The older-style Mercer indicators, pre-2001, were made in England. All subsequent Swiss models carry the suffix -1 on the model number. They were a big improvement over the old ones.
Mercer indicators which are metric will have yellow dials. This is the norm for the US and UK. Inch reading indicators will have standard white dials.
The Series 300 indicators come with a 1/4" mounting stem in a hard plastic box. Other size stems and attachments are available on page page 36. A serial number and declaration of conformity are included, but without calibration data.