It's trying to be some kind of cutting test, but everything is slightly wrong. Kyōhō is OK, but the date format is unusual. One would expect it to say 享保十一年三月 (Kyōhō13, 3rd Month) and not run them together as they are on your sword. With the numbers running together, it causes confusion about which year and which month is written. On your sword its OK because we know there is no 13th Month, but the possibility for confusion is great, so that is why you never see this format. Or, I should say I've never seen this format before.
Next, the date is carved high up into the sword blade (the polished part), instead of on the nakago. This is also highly unusual.
After that, I can't really read it. The character 胴 (body) is clear enough, but all the other characters are unusual. There is a mixture of grass script, normal script, which is also strange. I would be suspicious of this sword unless it has authentication papers. However, if it had authentication papers, the appraisers would have written down the inscription on the authentication certificate.