You may have seen multiple aircraft carrying designations that look like this, "X-05, C-08, P-49" or others, but what do they mean.
To cut to the chase we use the USAAF numbering system, even on civilian aircraft. C-XX For Cargo, X-XX for experimental, etc. BP typically indicates civilian aircraft, but a passenger designation is currently being adopted. As for the numbers, they typically designate the year the aircraft was either tested or put into service/on the civilian market. As for aircraft that lack a designation, such as the Bee or first 3 Bertha's, they typically designate a line of aircraft with successors built within the 10 years of each other, with variants typically gaining official designations, such as the P-128. With the Bee, as tradition none of them will receive official designations, simply because a numeric code doesn't sum up how weird it is. Land vehicles rarely receive this, such as No.1, the original locomotive used, although racecars do on insistence of the PR department.