In some forums, posts are labeled with a date and a unique number. For example, "bt2016" as the initials or identifier for a user or group, then the date, revision, and subject. But that's speculative.
I should also consider other possibilities. For instance, "BT" in a different context could refer to a company or department within a company. If this is a part number, perhaps in manufacturing or software, the format bt2016r73146ultsc could denote a product from 2016 with a specific revision and series (ULTSC). bt2016r73146ultsc
Next, "r73146" – "r" is commonly used as a prefix for revision numbers. So "r73146" would be revision 73146. That makes sense in technical contexts where documents or products have multiple revisions. In some forums, posts are labeled with a