It is possible to prepare exhibits of telegrams and telegraphic services and enter these is philatelic exhibitions.
The appropriate class, according to the FIP Postal History Commission, is:
Class 2: Postal history.
2C: Historical, social and special studies.
Several examples of displays which fit Class 2 are provided in the Commission's review of judging a Postal History exhibit - the first example being TELEGRAM SERVICES.
Exhibits concentrating on the date stamps used on telegrams and in association with telegraphic services might, according to the FIP Postal History Commission and depending on how the exhibit was handled, be possible to enter into:
Class 2: Postal history.
2B: Marcophily - (showing classifications and/or studies of postal markings).
Full details of the requirements of an entry in Class 2B or Class 2C are provided on the official Commission site.
Unfortunately, although the change to rules were introduced in 2009, many judges are still not aware of the fact that telegrams and telegraphic services are classified there. These judges then move an entry to another class - especially Traditional or Thematic - and then apply inappropriate judging criteria to the telegraphic entry. I note such changes based on bitter personal experience both in Australia and in overseas philatelic exhibitions.