In my opinion, .ldr is wrong and .mpd is correct.
Please refer LDraw.org Standards: Official Model Repository (OMR) Specification Version 1.0.3
Has been discussed here before: https://forums.ldraw.org/thread-23070.html
Excerpt from the OMR Specification:
Base File Naming
Each model in the OMR will consist of several files that are packaged together into a single MPD file. For sets that include instructions for multiple models, each model will have its own MPD file. Each MPD for the set will be named in the following manner:
Where:
: The number assigned on the container of the set.
: Is a sequential number, starting with 2.
: The name of the set printed on the container in English.
: This is Optional in most cases. This is required for alternate models that are detailed in instructions (e.g. the Creator theme). In this case the naming is left to the discretion of the author but should be descriptive of the model contained in the MPD.
The
is not mandatory and gets added only if there is more than one set that could be assigned the same
. The first set using a given number would be understood to never contain the qualifier however numbering should start with the oldest set and some investigation should be done in existing set databases.
Example:
For playsets or other sets where there are multiple models that are part of an integral whole, all of the submodels will be contained in one MPD.
Example:
The creator set 4896 - Roaring Roadsters has 3 models in the instructions:
Please refer LDraw.org Standards: Official Model Repository (OMR) Specification Version 1.0.3
Has been discussed here before: https://forums.ldraw.org/thread-23070.html
Excerpt from the OMR Specification:
Base File Naming
Each model in the OMR will consist of several files that are packaged together into a single MPD file. For sets that include instructions for multiple models, each model will have its own MPD file. Each MPD for the set will be named in the following manner:
Code:
<Set Number>[-<Optional Qualifier>] - <Set Name>[ - <Sub Model Name>]
Code:
<Set Number>
Code:
<Optional Qualifier>
Code:
<Set Name>
Code:
<Sub Model Name>
The
Code:
<Optional Qualifier>
Code:
<Set Number>
Example:
Code:
6901 - Mobile Lab.mpd (Produced in 1980)
6901-2 - Space Plane.mpd (Produced in 1998)
Example:
The creator set 4896 - Roaring Roadsters has 3 models in the instructions:
Code:
4896 - Roaring Roadsters - Roadster.mpd
4896 - Roaring Roadsters - Dragster.mpd
4896 - Roaring Roadsters - SUV.mpd
If nothing goes right, go left.