From GRFSpecs

Template for a small icon indicating support by OpenTTD and TTDPatch or not.

No support {{ottdp}} Not supported by OpenTTD Not supported by TTDPatch
Support, version unknown {{ottdp|??|??}} Supported by OpenTTD ???? Supported by TTDPatch ????
⩾ OpenTTD 0.6 (r13923), No TTDPatch {{ottdp|0.6|ottdrev=r13923}} Supported by OpenTTD 0.6 (r13923)0.6 Not supported by TTDPatch
⩾ OpenTTD 0.7, No TTDPatch {{ottdp|0.7}} Supported by OpenTTD 0.70.7 Not supported by TTDPatch
⩾ OpenTTD 0.6 (r13923), TTDPatch 2.0.1 alpha 3 {{ottdp|0.6|2.5|ottdrev=r13923|ttdprev=2.0.1 alpha 3}} Supported by OpenTTD 0.6 (r13923)0.6 Supported by TTDPatch 2.5 (2.0.1 alpha 3)2.5
⩾ no OpenTTD, TTDPatch 2.5 beta 9 {{ottdp|no|2.5|ttdprev=beta 9}} Not supported by OpenTTD Supported by TTDPatch 2.5 (beta 9)2.5
⩾ OpenTTD 1.1, No TTDPatch {{ottdp|1.1}} Supported by OpenTTD 1.11.1 Not supported by TTDPatch
⩾ OpenTTD 1.2, No TTDPatch {{ottdp|1.2}} Supported by OpenTTD 1.21.2 Not supported by TTDPatch

Please only use version number of stable releases. You can put explicit revision numbers in the optional parameters "ottdrev" and "ttdprev", they will appear in the hoover text. Never use the term "nightly", use the expected number of the next release for features which are not yet part of a stable release.

Note, that NewGRF support before version 0.6 had misbehaviours in a general sense, which makes it hard to decide whether something was supported, or only worked in some cases. Thus we just do not document anything that might also have worked before 0.6.

Note that the next stable release to "TTDPatch 2.0.1 alpha xy" is actually "TTDPatch 2.5".