Version 18.104.22.168.1.7 and 22.214.171.124.0.1 both were able to open a v1.5 showfile (and higher) and save them back to a v1.4 compatible showfile format.
This isn't really recommended, as there is a lot of information that is now included in showfiles (1.9.8 added Pixel Mapping, 2.0 added magic sheets, etc...) that weren't there before. However, this process was mentioned as something Tech Services could do in release notes for several years following 1.5 and ending in 2.1.2.
The method (untested at the time of article writing in 2014, but it was tested back during 1.4.6 and 1.5 development):
- Install 126.96.36.199.1.7 or 1.4.6 on an offline PC
- Open the showfile. It may be advisable to open and save this in 1.5 to strip out extra unknown data.
- Save the showfile. This will now be in a 1.4x format.
Both versions mentioned above are available in Team Central under Tech Services -> Software -> Eos Family -> Eos 1.5 to 1.4x Showfile Downconvert.