There are large numbers of varieties that fit into the description of Roma or San Marzano styles, and those two well known varieties are now used more to represent the style and include things like Amish Paste, Sausage, and a long list. They are typically elongated as you have pictured, have a high flesh to seed ratio and distinct seed compartments that allow for easier separation of seed and flesh. Most also have less juice than many tomatoes not intended for pastes and sauces and are typically marketed as paste tomatoes. San Marzano is probably considered by most the classic with Roma well known and a bit more of a cross-over used often fresh in salads as well. The many other varieties are attempts to improve productivity, increase sizes, stretch the season, add disease resistance and adapt to climates. Most will compare their taste to the San Marzano as the standard though, and if your can is a product of Italy, their is a good chance that variety was used or one of its very close crosses as traditional farmers tend to be very reluctant to change off of traditional varieties.
ETA: From comments, it appears that restrictions on the San Marzano labeling is fro the DPO label which restricts production to only the Valley del Sarno region, and those do indeed carry a very high price and hefty fines for fraud. Other Italian produced SM's are still premium priced but much more reasonably at least in the US. That would tend to indicate more moderately priced would be a mix or another relative attempting to get close to the same taste, while possibly picking up some advantages like determinant nature of plant and more modern disease resistance.
